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Built-in Types — Python 3.6.7 documentation</title> <link rel="stylesheet" href="../_static/pydoctheme.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript" id="documentation_options" data-url_root="../" src="../_static/documentation_options.js"></script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/sidebar.js"></script> <link rel="search" type="application/opensearchdescription+xml" title="Search within Python 3.6.7 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="next" title="5. Built-in Exceptions" href="exceptions.html" /> <link rel="prev" title="3. Built-in Constants" href="constants.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/3/library/stdtypes.html" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head><body> <div class="related" role="navigation" aria-label="related navigation"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="../genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="exceptions.html" title="5. Built-in Exceptions" accesskey="N">next</a> |</li> <li class="right" > <a href="constants.html" title="3. Built-in Constants" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="https://www.python.org/">Python</a> »</li> <li> <a href="../index.html">3.6.7 Documentation</a> » </li> <li class="nav-item nav-item-1"><a href="index.html" accesskey="U">The Python Standard Library</a> »</li> <li class="right"> <div class="inline-search" style="display: none" role="search"> <form class="inline-search" action="../search.html" method="get"> <input placeholder="Quick search" type="text" name="q" /> <input type="submit" value="Go" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> <script type="text/javascript">$('.inline-search').show(0);</script> | </li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body" role="main"> <div class="section" id="built-in-types"> <span id="bltin-types"></span><h1>4. Built-in Types<a class="headerlink" href="#built-in-types" title="Permalink to this headline">¶</a></h1> <p>The following sections describe the standard types that are built into the interpreter.</p> <p id="index-0">The principal built-in types are numerics, sequences, mappings, classes, instances and exceptions.</p> <p>Some collection classes are mutable. The methods that add, subtract, or rearrange their members in place, and don’t return a specific item, never return the collection instance itself but <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> <p>Some operations are supported by several object types; in particular, practically all objects can be compared, tested for truth value, and converted to a string (with the <a class="reference internal" href="functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate"><span class="pre">repr()</span></code></a> function or the slightly different <a class="reference internal" href="#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> function). The latter function is implicitly used when an object is written by the <a class="reference internal" href="functions.html#print" title="print"><code class="xref py py-func docutils literal notranslate"><span class="pre">print()</span></code></a> function.</p> <div class="section" id="truth-value-testing"> <span id="truth"></span><h2>4.1. Truth Value Testing<a class="headerlink" href="#truth-value-testing" title="Permalink to this headline">¶</a></h2> <p id="index-1">Any object can be tested for truth value, for use in an <a class="reference internal" href="../reference/compound_stmts.html#if"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">if</span></code></a> or <a class="reference internal" href="../reference/compound_stmts.html#while"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">while</span></code></a> condition or as operand of the Boolean operations below.</p> <p id="index-2">By default, an object is considered true unless its class defines either a <a class="reference internal" href="../reference/datamodel.html#object.__bool__" title="object.__bool__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__bool__()</span></code></a> method that returns <code class="docutils literal notranslate"><span class="pre">False</span></code> or a <a class="reference internal" href="../reference/datamodel.html#object.__len__" title="object.__len__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__len__()</span></code></a> method that returns zero, when called with the object. <a class="footnote-reference" href="#id12" id="id1">[1]</a> Here are most of the built-in objects considered false:</p> <blockquote> <div></div></blockquote> <ul class="simple" id="index-3"> <li>constants defined to be false: <code class="docutils literal notranslate"><span class="pre">None</span></code> and <code class="docutils literal notranslate"><span class="pre">False</span></code>.</li> <li>zero of any numeric type: <code class="docutils literal notranslate"><span class="pre">0</span></code>, <code class="docutils literal notranslate"><span class="pre">0.0</span></code>, <code class="docutils literal notranslate"><span class="pre">0j</span></code>, <code class="docutils literal notranslate"><span class="pre">Decimal(0)</span></code>, <code class="docutils literal notranslate"><span class="pre">Fraction(0,</span> <span class="pre">1)</span></code></li> <li>empty sequences and collections: <code class="docutils literal notranslate"><span class="pre">''</span></code>, <code class="docutils literal notranslate"><span class="pre">()</span></code>, <code class="docutils literal notranslate"><span class="pre">[]</span></code>, <code class="docutils literal notranslate"><span class="pre">{}</span></code>, <code class="docutils literal notranslate"><span class="pre">set()</span></code>, <code class="docutils literal notranslate"><span class="pre">range(0)</span></code></li> </ul> <p id="index-4">Operations and built-in functions that have a Boolean result always return <code class="docutils literal notranslate"><span class="pre">0</span></code> or <code class="docutils literal notranslate"><span class="pre">False</span></code> for false and <code class="docutils literal notranslate"><span class="pre">1</span></code> or <code class="docutils literal notranslate"><span class="pre">True</span></code> for true, unless otherwise stated. (Important exception: the Boolean operations <code class="docutils literal notranslate"><span class="pre">or</span></code> and <code class="docutils literal notranslate"><span class="pre">and</span></code> always return one of their operands.)</p> </div> <div class="section" id="boolean-operations-and-or-not"> <span id="boolean"></span><h2>4.2. Boolean Operations — <a class="reference internal" href="../reference/expressions.html#and"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">and</span></code></a>, <a class="reference internal" href="../reference/expressions.html#or"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">or</span></code></a>, <a class="reference internal" href="../reference/expressions.html#not"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">not</span></code></a><a class="headerlink" href="#boolean-operations-and-or-not" title="Permalink to this headline">¶</a></h2> <p id="index-5">These are the Boolean operations, ordered by ascending priority:</p> <table border="1" class="docutils"> <colgroup> <col width="25%" /> <col width="62%" /> <col width="13%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Result</th> <th class="head">Notes</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">or</span> <span class="pre">y</span></code></td> <td>if <em>x</em> is false, then <em>y</em>, else <em>x</em></td> <td>(1)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">and</span> <span class="pre">y</span></code></td> <td>if <em>x</em> is false, then <em>x</em>, else <em>y</em></td> <td>(2)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">not</span> <span class="pre">x</span></code></td> <td>if <em>x</em> is false, then <code class="docutils literal notranslate"><span class="pre">True</span></code>, else <code class="docutils literal notranslate"><span class="pre">False</span></code></td> <td>(3)</td> </tr> </tbody> </table> <p id="index-6">Notes:</p> <ol class="arabic simple"> <li>This is a short-circuit operator, so it only evaluates the second argument if the first one is false.</li> <li>This is a short-circuit operator, so it only evaluates the second argument if the first one is true.</li> <li><code class="docutils literal notranslate"><span class="pre">not</span></code> has a lower priority than non-Boolean operators, so <code class="docutils literal notranslate"><span class="pre">not</span> <span class="pre">a</span> <span class="pre">==</span> <span class="pre">b</span></code> is interpreted as <code class="docutils literal notranslate"><span class="pre">not</span> <span class="pre">(a</span> <span class="pre">==</span> <span class="pre">b)</span></code>, and <code class="docutils literal notranslate"><span class="pre">a</span> <span class="pre">==</span> <span class="pre">not</span> <span class="pre">b</span></code> is a syntax error.</li> </ol> </div> <div class="section" id="comparisons"> <span id="stdcomparisons"></span><h2>4.3. Comparisons<a class="headerlink" href="#comparisons" title="Permalink to this headline">¶</a></h2> <p id="index-7">There are eight comparison operations in Python. They all have the same priority (which is higher than that of the Boolean operations). Comparisons can be chained arbitrarily; for example, <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre"><</span> <span class="pre">y</span> <span class="pre"><=</span> <span class="pre">z</span></code> is equivalent to <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre"><</span> <span class="pre">y</span> <span class="pre">and</span> <span class="pre">y</span> <span class="pre"><=</span> <span class="pre">z</span></code>, except that <em>y</em> is evaluated only once (but in both cases <em>z</em> is not evaluated at all when <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre"><</span> <span class="pre">y</span></code> is found to be false).</p> <p>This table summarizes the comparison operations:</p> <table border="1" class="docutils"> <colgroup> <col width="32%" /> <col width="68%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Meaning</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre"><</span></code></td> <td>strictly less than</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre"><=</span></code></td> <td>less than or equal</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">></span></code></td> <td>strictly greater than</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">>=</span></code></td> <td>greater than or equal</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">==</span></code></td> <td>equal</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">!=</span></code></td> <td>not equal</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">is</span></code></td> <td>object identity</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">is</span> <span class="pre">not</span></code></td> <td>negated object identity</td> </tr> </tbody> </table> <p id="index-8">Objects of different types, except different numeric types, never compare equal. Furthermore, some types (for example, function objects) support only a degenerate notion of comparison where any two objects of that type are unequal. The <code class="docutils literal notranslate"><span class="pre"><</span></code>, <code class="docutils literal notranslate"><span class="pre"><=</span></code>, <code class="docutils literal notranslate"><span class="pre">></span></code> and <code class="docutils literal notranslate"><span class="pre">>=</span></code> operators will raise a <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> exception when comparing a complex number with another built-in numeric type, when the objects are of different types that cannot be compared, or in other cases where there is no defined ordering.</p> <p id="index-9">Non-identical instances of a class normally compare as non-equal unless the class defines the <a class="reference internal" href="../reference/datamodel.html#object.__eq__" title="object.__eq__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__eq__()</span></code></a> method.</p> <p>Instances of a class cannot be ordered with respect to other instances of the same class, or other types of object, unless the class defines enough of the methods <a class="reference internal" href="../reference/datamodel.html#object.__lt__" title="object.__lt__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__lt__()</span></code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__le__" title="object.__le__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__le__()</span></code></a>, <a class="reference internal" href="../reference/datamodel.html#object.__gt__" title="object.__gt__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__gt__()</span></code></a>, and <a class="reference internal" href="../reference/datamodel.html#object.__ge__" title="object.__ge__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__ge__()</span></code></a> (in general, <a class="reference internal" href="../reference/datamodel.html#object.__lt__" title="object.__lt__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__lt__()</span></code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__eq__" title="object.__eq__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__eq__()</span></code></a> are sufficient, if you want the conventional meanings of the comparison operators).</p> <p>The behavior of the <a class="reference internal" href="../reference/expressions.html#is"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">is</span></code></a> and <a class="reference internal" href="../reference/expressions.html#is-not"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">is</span> <span class="pre">not</span></code></a> operators cannot be customized; also they can be applied to any two objects and never raise an exception.</p> <p id="index-10">Two more operations with the same syntactic priority, <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">in</span></code></a> and <a class="reference internal" href="../reference/expressions.html#not-in"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">not</span> <span class="pre">in</span></code></a>, are supported by types that are <a class="reference internal" href="../glossary.html#term-iterable"><span class="xref std std-term">iterable</span></a> or implement the <a class="reference internal" href="../reference/datamodel.html#object.__contains__" title="object.__contains__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__contains__()</span></code></a> method.</p> </div> <div class="section" id="numeric-types-int-float-complex"> <span id="typesnumeric"></span><h2>4.4. Numeric Types — <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a><a class="headerlink" href="#numeric-types-int-float-complex" title="Permalink to this headline">¶</a></h2> <p id="index-11">There are three distinct numeric types: <em class="dfn">integers</em>, <em class="dfn">floating point numbers</em>, and <em class="dfn">complex numbers</em>. In addition, Booleans are a subtype of integers. Integers have unlimited precision. Floating point numbers are usually implemented using <code class="xref c c-type docutils literal notranslate"><span class="pre">double</span></code> in C; information about the precision and internal representation of floating point numbers for the machine on which your program is running is available in <a class="reference internal" href="sys.html#sys.float_info" title="sys.float_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.float_info</span></code></a>. Complex numbers have a real and imaginary part, which are each a floating point number. To extract these parts from a complex number <em>z</em>, use <code class="docutils literal notranslate"><span class="pre">z.real</span></code> and <code class="docutils literal notranslate"><span class="pre">z.imag</span></code>. (The standard library includes additional numeric types, <a class="reference internal" href="fractions.html#module-fractions" title="fractions: Rational numbers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">fractions</span></code></a> that hold rationals, and <a class="reference internal" href="decimal.html#module-decimal" title="decimal: Implementation of the General Decimal Arithmetic Specification."><code class="xref py py-mod docutils literal notranslate"><span class="pre">decimal</span></code></a> that hold floating-point numbers with user-definable precision.)</p> <p id="index-12">Numbers are created by numeric literals or as the result of built-in functions and operators. Unadorned integer literals (including hex, octal and binary numbers) yield integers. Numeric literals containing a decimal point or an exponent sign yield floating point numbers. Appending <code class="docutils literal notranslate"><span class="pre">'j'</span></code> or <code class="docutils literal notranslate"><span class="pre">'J'</span></code> to a numeric literal yields an imaginary number (a complex number with a zero real part) which you can add to an integer or float to get a complex number with real and imaginary parts.</p> <p id="index-13">Python fully supports mixed arithmetic: when a binary arithmetic operator has operands of different numeric types, the operand with the “narrower” type is widened to that of the other, where integer is narrower than floating point, which is narrower than complex. Comparisons between numbers of mixed type use the same rule. <a class="footnote-reference" href="#id13" id="id2">[2]</a> The constructors <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-func docutils literal notranslate"><span class="pre">int()</span></code></a>, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-func docutils literal notranslate"><span class="pre">float()</span></code></a>, and <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-func docutils literal notranslate"><span class="pre">complex()</span></code></a> can be used to produce numbers of a specific type.</p> <p>All numeric types (except complex) support the following operations, sorted by ascending priority (all numeric operations have a higher priority than comparison operations):</p> <table border="1" class="docutils"> <colgroup> <col width="25%" /> <col width="40%" /> <col width="11%" /> <col width="24%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Result</th> <th class="head">Notes</th> <th class="head">Full documentation</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">+</span> <span class="pre">y</span></code></td> <td>sum of <em>x</em> and <em>y</em></td> <td> </td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">-</span> <span class="pre">y</span></code></td> <td>difference of <em>x</em> and <em>y</em></td> <td> </td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">*</span> <span class="pre">y</span></code></td> <td>product of <em>x</em> and <em>y</em></td> <td> </td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">/</span> <span class="pre">y</span></code></td> <td>quotient of <em>x</em> and <em>y</em></td> <td> </td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">//</span> <span class="pre">y</span></code></td> <td>floored quotient of <em>x</em> and <em>y</em></td> <td>(1)</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">%</span> <span class="pre">y</span></code></td> <td>remainder of <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">/</span> <span class="pre">y</span></code></td> <td>(2)</td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">-x</span></code></td> <td><em>x</em> negated</td> <td> </td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">+x</span></code></td> <td><em>x</em> unchanged</td> <td> </td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">abs(x)</span></code></td> <td>absolute value or magnitude of <em>x</em></td> <td> </td> <td><a class="reference internal" href="functions.html#abs" title="abs"><code class="xref py py-func docutils literal notranslate"><span class="pre">abs()</span></code></a></td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">int(x)</span></code></td> <td><em>x</em> converted to integer</td> <td>(3)(6)</td> <td><a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-func docutils literal notranslate"><span class="pre">int()</span></code></a></td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">float(x)</span></code></td> <td><em>x</em> converted to floating point</td> <td>(4)(6)</td> <td><a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-func docutils literal notranslate"><span class="pre">float()</span></code></a></td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">complex(re,</span> <span class="pre">im)</span></code></td> <td>a complex number with real part <em>re</em>, imaginary part <em>im</em>. <em>im</em> defaults to zero.</td> <td>(6)</td> <td><a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-func docutils literal notranslate"><span class="pre">complex()</span></code></a></td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">c.conjugate()</span></code></td> <td>conjugate of the complex number <em>c</em></td> <td> </td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">divmod(x,</span> <span class="pre">y)</span></code></td> <td>the pair <code class="docutils literal notranslate"><span class="pre">(x</span> <span class="pre">//</span> <span class="pre">y,</span> <span class="pre">x</span> <span class="pre">%</span> <span class="pre">y)</span></code></td> <td>(2)</td> <td><a class="reference internal" href="functions.html#divmod" title="divmod"><code class="xref py py-func docutils literal notranslate"><span class="pre">divmod()</span></code></a></td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">pow(x,</span> <span class="pre">y)</span></code></td> <td><em>x</em> to the power <em>y</em></td> <td>(5)</td> <td><a class="reference internal" href="functions.html#pow" title="pow"><code class="xref py py-func docutils literal notranslate"><span class="pre">pow()</span></code></a></td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">**</span> <span class="pre">y</span></code></td> <td><em>x</em> to the power <em>y</em></td> <td>(5)</td> <td> </td> </tr> </tbody> </table> <p id="index-14">Notes:</p> <ol class="arabic"> <li><p class="first">Also referred to as integer division. The resultant value is a whole integer, though the result’s type is not necessarily int. The result is always rounded towards minus infinity: <code class="docutils literal notranslate"><span class="pre">1//2</span></code> is <code class="docutils literal notranslate"><span class="pre">0</span></code>, <code class="docutils literal notranslate"><span class="pre">(-1)//2</span></code> is <code class="docutils literal notranslate"><span class="pre">-1</span></code>, <code class="docutils literal notranslate"><span class="pre">1//(-2)</span></code> is <code class="docutils literal notranslate"><span class="pre">-1</span></code>, and <code class="docutils literal notranslate"><span class="pre">(-1)//(-2)</span></code> is <code class="docutils literal notranslate"><span class="pre">0</span></code>.</p> </li> <li><p class="first">Not for complex numbers. Instead convert to floats using <a class="reference internal" href="functions.html#abs" title="abs"><code class="xref py py-func docutils literal notranslate"><span class="pre">abs()</span></code></a> if appropriate.</p> </li> <li><p id="index-15">Conversion from floating point to integer may round or truncate as in C; see functions <a class="reference internal" href="math.html#math.floor" title="math.floor"><code class="xref py py-func docutils literal notranslate"><span class="pre">math.floor()</span></code></a> and <a class="reference internal" href="math.html#math.ceil" title="math.ceil"><code class="xref py py-func docutils literal notranslate"><span class="pre">math.ceil()</span></code></a> for well-defined conversions.</p> </li> <li><p class="first">float also accepts the strings “nan” and “inf” with an optional prefix “+” or “-” for Not a Number (NaN) and positive or negative infinity.</p> </li> <li><p class="first">Python defines <code class="docutils literal notranslate"><span class="pre">pow(0,</span> <span class="pre">0)</span></code> and <code class="docutils literal notranslate"><span class="pre">0</span> <span class="pre">**</span> <span class="pre">0</span></code> to be <code class="docutils literal notranslate"><span class="pre">1</span></code>, as is common for programming languages.</p> </li> <li><p class="first">The numeric literals accepted include the digits <code class="docutils literal notranslate"><span class="pre">0</span></code> to <code class="docutils literal notranslate"><span class="pre">9</span></code> or any Unicode equivalent (code points with the <code class="docutils literal notranslate"><span class="pre">Nd</span></code> property).</p> <p>See <a class="reference external" href="http://www.unicode.org/Public/9.0.0/ucd/extracted/DerivedNumericType.txt">http://www.unicode.org/Public/9.0.0/ucd/extracted/DerivedNumericType.txt</a> for a complete list of code points with the <code class="docutils literal notranslate"><span class="pre">Nd</span></code> property.</p> </li> </ol> <p>All <a class="reference internal" href="numbers.html#numbers.Real" title="numbers.Real"><code class="xref py py-class docutils literal notranslate"><span class="pre">numbers.Real</span></code></a> types (<a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a> and <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>) also include the following operations:</p> <table border="1" class="docutils"> <colgroup> <col width="31%" /> <col width="69%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Result</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><a class="reference internal" href="math.html#math.trunc" title="math.trunc"><code class="xref py py-func docutils literal notranslate"><span class="pre">math.trunc(x)</span></code></a></td> <td><em>x</em> truncated to <a class="reference internal" href="numbers.html#numbers.Integral" title="numbers.Integral"><code class="xref py py-class docutils literal notranslate"><span class="pre">Integral</span></code></a></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="functions.html#round" title="round"><code class="xref py py-func docutils literal notranslate"><span class="pre">round(x[,</span> <span class="pre">n])</span></code></a></td> <td><em>x</em> rounded to <em>n</em> digits, rounding half to even. If <em>n</em> is omitted, it defaults to 0.</td> </tr> <tr class="row-even"><td><a class="reference internal" href="math.html#math.floor" title="math.floor"><code class="xref py py-func docutils literal notranslate"><span class="pre">math.floor(x)</span></code></a></td> <td>the greatest <a class="reference internal" href="numbers.html#numbers.Integral" title="numbers.Integral"><code class="xref py py-class docutils literal notranslate"><span class="pre">Integral</span></code></a> <= <em>x</em></td> </tr> <tr class="row-odd"><td><a class="reference internal" href="math.html#math.ceil" title="math.ceil"><code class="xref py py-func docutils literal notranslate"><span class="pre">math.ceil(x)</span></code></a></td> <td>the least <a class="reference internal" href="numbers.html#numbers.Integral" title="numbers.Integral"><code class="xref py py-class docutils literal notranslate"><span class="pre">Integral</span></code></a> >= <em>x</em></td> </tr> </tbody> </table> <p>For additional numeric operations see the <a class="reference internal" href="math.html#module-math" title="math: Mathematical functions (sin() etc.)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">math</span></code></a> and <a class="reference internal" href="cmath.html#module-cmath" title="cmath: Mathematical functions for complex numbers."><code class="xref py py-mod docutils literal notranslate"><span class="pre">cmath</span></code></a> modules.</p> <div class="section" id="bitwise-operations-on-integer-types"> <span id="bitstring-ops"></span><h3>4.4.1. Bitwise Operations on Integer Types<a class="headerlink" href="#bitwise-operations-on-integer-types" title="Permalink to this headline">¶</a></h3> <p id="index-16">Bitwise operations only make sense for integers. The result of bitwise operations is calculated as though carried out in two’s complement with an infinite number of sign bits.</p> <p>The priorities of the binary bitwise operations are all lower than the numeric operations and higher than the comparisons; the unary operation <code class="docutils literal notranslate"><span class="pre">~</span></code> has the same priority as the other unary numeric operations (<code class="docutils literal notranslate"><span class="pre">+</span></code> and <code class="docutils literal notranslate"><span class="pre">-</span></code>).</p> <p>This table lists the bitwise operations sorted in ascending priority:</p> <table border="1" class="docutils"> <colgroup> <col width="22%" /> <col width="59%" /> <col width="19%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Result</th> <th class="head">Notes</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">|</span> <span class="pre">y</span></code></td> <td>bitwise <em class="dfn">or</em> of <em>x</em> and <em>y</em></td> <td>(4)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">^</span> <span class="pre">y</span></code></td> <td>bitwise <em class="dfn">exclusive or</em> of <em>x</em> and <em>y</em></td> <td>(4)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">&</span> <span class="pre">y</span></code></td> <td>bitwise <em class="dfn">and</em> of <em>x</em> and <em>y</em></td> <td>(4)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre"><<</span> <span class="pre">n</span></code></td> <td><em>x</em> shifted left by <em>n</em> bits</td> <td>(1)(2)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">>></span> <span class="pre">n</span></code></td> <td><em>x</em> shifted right by <em>n</em> bits</td> <td>(1)(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">~x</span></code></td> <td>the bits of <em>x</em> inverted</td> <td> </td> </tr> </tbody> </table> <p>Notes:</p> <ol class="arabic simple"> <li>Negative shift counts are illegal and cause a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> to be raised.</li> <li>A left shift by <em>n</em> bits is equivalent to multiplication by <code class="docutils literal notranslate"><span class="pre">pow(2,</span> <span class="pre">n)</span></code> without overflow check.</li> <li>A right shift by <em>n</em> bits is equivalent to division by <code class="docutils literal notranslate"><span class="pre">pow(2,</span> <span class="pre">n)</span></code> without overflow check.</li> <li>Performing these calculations with at least one extra sign extension bit in a finite two’s complement representation (a working bit-width of <code class="docutils literal notranslate"><span class="pre">1</span> <span class="pre">+</span> <span class="pre">max(x.bit_length(),</span> <span class="pre">y.bit_length()</span></code> or more) is sufficient to get the same result as if there were an infinite number of sign bits.</li> </ol> </div> <div class="section" id="additional-methods-on-integer-types"> <h3>4.4.2. Additional Methods on Integer Types<a class="headerlink" href="#additional-methods-on-integer-types" title="Permalink to this headline">¶</a></h3> <p>The int type implements the <a class="reference internal" href="numbers.html#numbers.Integral" title="numbers.Integral"><code class="xref py py-class docutils literal notranslate"><span class="pre">numbers.Integral</span></code></a> <a class="reference internal" href="../glossary.html#term-abstract-base-class"><span class="xref std std-term">abstract base class</span></a>. In addition, it provides a few more methods:</p> <dl class="method"> <dt id="int.bit_length"> <code class="descclassname">int.</code><code class="descname">bit_length</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#int.bit_length" title="Permalink to this definition">¶</a></dt> <dd><p>Return the number of bits necessary to represent an integer in binary, excluding the sign and leading zeros:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">n</span> <span class="o">=</span> <span class="o">-</span><span class="mi">37</span> <span class="gp">>>> </span><span class="nb">bin</span><span class="p">(</span><span class="n">n</span><span class="p">)</span> <span class="go">'-0b100101'</span> <span class="gp">>>> </span><span class="n">n</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span> <span class="go">6</span> </pre></div> </div> <p>More precisely, if <code class="docutils literal notranslate"><span class="pre">x</span></code> is nonzero, then <code class="docutils literal notranslate"><span class="pre">x.bit_length()</span></code> is the unique positive integer <code class="docutils literal notranslate"><span class="pre">k</span></code> such that <code class="docutils literal notranslate"><span class="pre">2**(k-1)</span> <span class="pre"><=</span> <span class="pre">abs(x)</span> <span class="pre"><</span> <span class="pre">2**k</span></code>. Equivalently, when <code class="docutils literal notranslate"><span class="pre">abs(x)</span></code> is small enough to have a correctly rounded logarithm, then <code class="docutils literal notranslate"><span class="pre">k</span> <span class="pre">=</span> <span class="pre">1</span> <span class="pre">+</span> <span class="pre">int(log(abs(x),</span> <span class="pre">2))</span></code>. If <code class="docutils literal notranslate"><span class="pre">x</span></code> is zero, then <code class="docutils literal notranslate"><span class="pre">x.bit_length()</span></code> returns <code class="docutils literal notranslate"><span class="pre">0</span></code>.</p> <p>Equivalent to:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">bit_length</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <span class="n">s</span> <span class="o">=</span> <span class="nb">bin</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span> <span class="c1"># binary representation: bin(-37) --> '-0b100101'</span> <span class="n">s</span> <span class="o">=</span> <span class="n">s</span><span class="o">.</span><span class="n">lstrip</span><span class="p">(</span><span class="s1">'-0b'</span><span class="p">)</span> <span class="c1"># remove leading zeros and minus sign</span> <span class="k">return</span> <span class="nb">len</span><span class="p">(</span><span class="n">s</span><span class="p">)</span> <span class="c1"># len('100101') --> 6</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.1.</span></p> </div> </dd></dl> <dl class="method"> <dt id="int.to_bytes"> <code class="descclassname">int.</code><code class="descname">to_bytes</code><span class="sig-paren">(</span><em>length</em>, <em>byteorder</em>, <em>*</em>, <em>signed=False</em><span class="sig-paren">)</span><a class="headerlink" href="#int.to_bytes" title="Permalink to this definition">¶</a></dt> <dd><p>Return an array of bytes representing an integer.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="p">(</span><span class="mi">1024</span><span class="p">)</span><span class="o">.</span><span class="n">to_bytes</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">)</span> <span class="go">b'\x04\x00'</span> <span class="gp">>>> </span><span class="p">(</span><span class="mi">1024</span><span class="p">)</span><span class="o">.</span><span class="n">to_bytes</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">)</span> <span class="go">b'\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00'</span> <span class="gp">>>> </span><span class="p">(</span><span class="o">-</span><span class="mi">1024</span><span class="p">)</span><span class="o">.</span><span class="n">to_bytes</span><span class="p">(</span><span class="mi">10</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">,</span> <span class="n">signed</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="go">b'\xff\xff\xff\xff\xff\xff\xff\xff\xfc\x00'</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="mi">1000</span> <span class="gp">>>> </span><span class="n">x</span><span class="o">.</span><span class="n">to_bytes</span><span class="p">((</span><span class="n">x</span><span class="o">.</span><span class="n">bit_length</span><span class="p">()</span> <span class="o">+</span> <span class="mi">7</span><span class="p">)</span> <span class="o">//</span> <span class="mi">8</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'little'</span><span class="p">)</span> <span class="go">b'\xe8\x03'</span> </pre></div> </div> <p>The integer is represented using <em>length</em> bytes. An <a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a> is raised if the integer is not representable with the given number of bytes.</p> <p>The <em>byteorder</em> argument determines the byte order used to represent the integer. If <em>byteorder</em> is <code class="docutils literal notranslate"><span class="pre">"big"</span></code>, the most significant byte is at the beginning of the byte array. If <em>byteorder</em> is <code class="docutils literal notranslate"><span class="pre">"little"</span></code>, the most significant byte is at the end of the byte array. To request the native byte order of the host system, use <a class="reference internal" href="sys.html#sys.byteorder" title="sys.byteorder"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.byteorder</span></code></a> as the byte order value.</p> <p>The <em>signed</em> argument determines whether two’s complement is used to represent the integer. If <em>signed</em> is <code class="docutils literal notranslate"><span class="pre">False</span></code> and a negative integer is given, an <a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a> is raised. The default value for <em>signed</em> is <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.2.</span></p> </div> </dd></dl> <dl class="classmethod"> <dt id="int.from_bytes"> <em class="property">classmethod </em><code class="descclassname">int.</code><code class="descname">from_bytes</code><span class="sig-paren">(</span><em>bytes</em>, <em>byteorder</em>, <em>*</em>, <em>signed=False</em><span class="sig-paren">)</span><a class="headerlink" href="#int.from_bytes" title="Permalink to this definition">¶</a></dt> <dd><p>Return the integer represented by the given array of bytes.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\x00\x10</span><span class="s1">'</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">)</span> <span class="go">16</span> <span class="gp">>>> </span><span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\x00\x10</span><span class="s1">'</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'little'</span><span class="p">)</span> <span class="go">4096</span> <span class="gp">>>> </span><span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\xfc\x00</span><span class="s1">'</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">,</span> <span class="n">signed</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="go">-1024</span> <span class="gp">>>> </span><span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\xfc\x00</span><span class="s1">'</span><span class="p">,</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">,</span> <span class="n">signed</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span> <span class="go">64512</span> <span class="gp">>>> </span><span class="nb">int</span><span class="o">.</span><span class="n">from_bytes</span><span class="p">([</span><span class="mi">255</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">],</span> <span class="n">byteorder</span><span class="o">=</span><span class="s1">'big'</span><span class="p">)</span> <span class="go">16711680</span> </pre></div> </div> <p>The argument <em>bytes</em> must either be a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> or an iterable producing bytes.</p> <p>The <em>byteorder</em> argument determines the byte order used to represent the integer. If <em>byteorder</em> is <code class="docutils literal notranslate"><span class="pre">"big"</span></code>, the most significant byte is at the beginning of the byte array. If <em>byteorder</em> is <code class="docutils literal notranslate"><span class="pre">"little"</span></code>, the most significant byte is at the end of the byte array. To request the native byte order of the host system, use <a class="reference internal" href="sys.html#sys.byteorder" title="sys.byteorder"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.byteorder</span></code></a> as the byte order value.</p> <p>The <em>signed</em> argument indicates whether two’s complement is used to represent the integer.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.2.</span></p> </div> </dd></dl> </div> <div class="section" id="additional-methods-on-float"> <h3>4.4.3. Additional Methods on Float<a class="headerlink" href="#additional-methods-on-float" title="Permalink to this headline">¶</a></h3> <p>The float type implements the <a class="reference internal" href="numbers.html#numbers.Real" title="numbers.Real"><code class="xref py py-class docutils literal notranslate"><span class="pre">numbers.Real</span></code></a> <a class="reference internal" href="../glossary.html#term-abstract-base-class"><span class="xref std std-term">abstract base class</span></a>. float also has the following additional methods.</p> <dl class="method"> <dt id="float.as_integer_ratio"> <code class="descclassname">float.</code><code class="descname">as_integer_ratio</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#float.as_integer_ratio" title="Permalink to this definition">¶</a></dt> <dd><p>Return a pair of integers whose ratio is exactly equal to the original float and with a positive denominator. Raises <a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a> on infinities and a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> on NaNs.</p> </dd></dl> <dl class="method"> <dt id="float.is_integer"> <code class="descclassname">float.</code><code class="descname">is_integer</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#float.is_integer" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the float instance is finite with integral value, and <code class="docutils literal notranslate"><span class="pre">False</span></code> otherwise:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="p">(</span><span class="o">-</span><span class="mf">2.0</span><span class="p">)</span><span class="o">.</span><span class="n">is_integer</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="p">(</span><span class="mf">3.2</span><span class="p">)</span><span class="o">.</span><span class="n">is_integer</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> </dd></dl> <p>Two methods support conversion to and from hexadecimal strings. Since Python’s floats are stored internally as binary numbers, converting a float to or from a <em>decimal</em> string usually involves a small rounding error. In contrast, hexadecimal strings allow exact representation and specification of floating-point numbers. This can be useful when debugging, and in numerical work.</p> <dl class="method"> <dt id="float.hex"> <code class="descclassname">float.</code><code class="descname">hex</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#float.hex" title="Permalink to this definition">¶</a></dt> <dd><p>Return a representation of a floating-point number as a hexadecimal string. For finite floating-point numbers, this representation will always include a leading <code class="docutils literal notranslate"><span class="pre">0x</span></code> and a trailing <code class="docutils literal notranslate"><span class="pre">p</span></code> and exponent.</p> </dd></dl> <dl class="classmethod"> <dt id="float.fromhex"> <em class="property">classmethod </em><code class="descclassname">float.</code><code class="descname">fromhex</code><span class="sig-paren">(</span><em>s</em><span class="sig-paren">)</span><a class="headerlink" href="#float.fromhex" title="Permalink to this definition">¶</a></dt> <dd><p>Class method to return the float represented by a hexadecimal string <em>s</em>. The string <em>s</em> may have leading and trailing whitespace.</p> </dd></dl> <p>Note that <a class="reference internal" href="#float.hex" title="float.hex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">float.hex()</span></code></a> is an instance method, while <a class="reference internal" href="#float.fromhex" title="float.fromhex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">float.fromhex()</span></code></a> is a class method.</p> <p>A hexadecimal string takes the form:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">[</span><span class="n">sign</span><span class="p">]</span> <span class="p">[</span><span class="s1">'0x'</span><span class="p">]</span> <span class="n">integer</span> <span class="p">[</span><span class="s1">'.'</span> <span class="n">fraction</span><span class="p">]</span> <span class="p">[</span><span class="s1">'p'</span> <span class="n">exponent</span><span class="p">]</span> </pre></div> </div> <p>where the optional <code class="docutils literal notranslate"><span class="pre">sign</span></code> may by either <code class="docutils literal notranslate"><span class="pre">+</span></code> or <code class="docutils literal notranslate"><span class="pre">-</span></code>, <code class="docutils literal notranslate"><span class="pre">integer</span></code> and <code class="docutils literal notranslate"><span class="pre">fraction</span></code> are strings of hexadecimal digits, and <code class="docutils literal notranslate"><span class="pre">exponent</span></code> is a decimal integer with an optional leading sign. Case is not significant, and there must be at least one hexadecimal digit in either the integer or the fraction. This syntax is similar to the syntax specified in section 6.4.4.2 of the C99 standard, and also to the syntax used in Java 1.5 onwards. In particular, the output of <a class="reference internal" href="#float.hex" title="float.hex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">float.hex()</span></code></a> is usable as a hexadecimal floating-point literal in C or Java code, and hexadecimal strings produced by C’s <code class="docutils literal notranslate"><span class="pre">%a</span></code> format character or Java’s <code class="docutils literal notranslate"><span class="pre">Double.toHexString</span></code> are accepted by <a class="reference internal" href="#float.fromhex" title="float.fromhex"><code class="xref py py-meth docutils literal notranslate"><span class="pre">float.fromhex()</span></code></a>.</p> <p>Note that the exponent is written in decimal rather than hexadecimal, and that it gives the power of 2 by which to multiply the coefficient. For example, the hexadecimal string <code class="docutils literal notranslate"><span class="pre">0x3.a7p10</span></code> represents the floating-point number <code class="docutils literal notranslate"><span class="pre">(3</span> <span class="pre">+</span> <span class="pre">10./16</span> <span class="pre">+</span> <span class="pre">7./16**2)</span> <span class="pre">*</span> <span class="pre">2.0**10</span></code>, or <code class="docutils literal notranslate"><span class="pre">3740.0</span></code>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">float</span><span class="o">.</span><span class="n">fromhex</span><span class="p">(</span><span class="s1">'0x3.a7p10'</span><span class="p">)</span> <span class="go">3740.0</span> </pre></div> </div> <p>Applying the reverse conversion to <code class="docutils literal notranslate"><span class="pre">3740.0</span></code> gives a different hexadecimal string representing the same number:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">float</span><span class="o">.</span><span class="n">hex</span><span class="p">(</span><span class="mf">3740.0</span><span class="p">)</span> <span class="go">'0x1.d380000000000p+11'</span> </pre></div> </div> </div> <div class="section" id="hashing-of-numeric-types"> <span id="numeric-hash"></span><h3>4.4.4. Hashing of numeric types<a class="headerlink" href="#hashing-of-numeric-types" title="Permalink to this headline">¶</a></h3> <p>For numbers <code class="docutils literal notranslate"><span class="pre">x</span></code> and <code class="docutils literal notranslate"><span class="pre">y</span></code>, possibly of different types, it’s a requirement that <code class="docutils literal notranslate"><span class="pre">hash(x)</span> <span class="pre">==</span> <span class="pre">hash(y)</span></code> whenever <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">==</span> <span class="pre">y</span></code> (see the <a class="reference internal" href="../reference/datamodel.html#object.__hash__" title="object.__hash__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__hash__()</span></code></a> method documentation for more details). For ease of implementation and efficiency across a variety of numeric types (including <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a> and <a class="reference internal" href="fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate"><span class="pre">fractions.Fraction</span></code></a>) Python’s hash for numeric types is based on a single mathematical function that’s defined for any rational number, and hence applies to all instances of <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a> and <a class="reference internal" href="fractions.html#fractions.Fraction" title="fractions.Fraction"><code class="xref py py-class docutils literal notranslate"><span class="pre">fractions.Fraction</span></code></a>, and all finite instances of <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a> and <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a>. Essentially, this function is given by reduction modulo <code class="docutils literal notranslate"><span class="pre">P</span></code> for a fixed prime <code class="docutils literal notranslate"><span class="pre">P</span></code>. The value of <code class="docutils literal notranslate"><span class="pre">P</span></code> is made available to Python as the <code class="xref py py-attr docutils literal notranslate"><span class="pre">modulus</span></code> attribute of <a class="reference internal" href="sys.html#sys.hash_info" title="sys.hash_info"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.hash_info</span></code></a>.</p> <div class="impl-detail compound"> <p><strong>CPython implementation detail:</strong> Currently, the prime used is <code class="docutils literal notranslate"><span class="pre">P</span> <span class="pre">=</span> <span class="pre">2**31</span> <span class="pre">-</span> <span class="pre">1</span></code> on machines with 32-bit C longs and <code class="docutils literal notranslate"><span class="pre">P</span> <span class="pre">=</span> <span class="pre">2**61</span> <span class="pre">-</span> <span class="pre">1</span></code> on machines with 64-bit C longs.</p> </div> <p>Here are the rules in detail:</p> <ul class="simple"> <li>If <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">=</span> <span class="pre">m</span> <span class="pre">/</span> <span class="pre">n</span></code> is a nonnegative rational number and <code class="docutils literal notranslate"><span class="pre">n</span></code> is not divisible by <code class="docutils literal notranslate"><span class="pre">P</span></code>, define <code class="docutils literal notranslate"><span class="pre">hash(x)</span></code> as <code class="docutils literal notranslate"><span class="pre">m</span> <span class="pre">*</span> <span class="pre">invmod(n,</span> <span class="pre">P)</span> <span class="pre">%</span> <span class="pre">P</span></code>, where <code class="docutils literal notranslate"><span class="pre">invmod(n,</span> <span class="pre">P)</span></code> gives the inverse of <code class="docutils literal notranslate"><span class="pre">n</span></code> modulo <code class="docutils literal notranslate"><span class="pre">P</span></code>.</li> <li>If <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">=</span> <span class="pre">m</span> <span class="pre">/</span> <span class="pre">n</span></code> is a nonnegative rational number and <code class="docutils literal notranslate"><span class="pre">n</span></code> is divisible by <code class="docutils literal notranslate"><span class="pre">P</span></code> (but <code class="docutils literal notranslate"><span class="pre">m</span></code> is not) then <code class="docutils literal notranslate"><span class="pre">n</span></code> has no inverse modulo <code class="docutils literal notranslate"><span class="pre">P</span></code> and the rule above doesn’t apply; in this case define <code class="docutils literal notranslate"><span class="pre">hash(x)</span></code> to be the constant value <code class="docutils literal notranslate"><span class="pre">sys.hash_info.inf</span></code>.</li> <li>If <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">=</span> <span class="pre">m</span> <span class="pre">/</span> <span class="pre">n</span></code> is a negative rational number define <code class="docutils literal notranslate"><span class="pre">hash(x)</span></code> as <code class="docutils literal notranslate"><span class="pre">-hash(-x)</span></code>. If the resulting hash is <code class="docutils literal notranslate"><span class="pre">-1</span></code>, replace it with <code class="docutils literal notranslate"><span class="pre">-2</span></code>.</li> <li>The particular values <code class="docutils literal notranslate"><span class="pre">sys.hash_info.inf</span></code>, <code class="docutils literal notranslate"><span class="pre">-sys.hash_info.inf</span></code> and <code class="docutils literal notranslate"><span class="pre">sys.hash_info.nan</span></code> are used as hash values for positive infinity, negative infinity, or nans (respectively). (All hashable nans have the same hash value.)</li> <li>For a <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a> number <code class="docutils literal notranslate"><span class="pre">z</span></code>, the hash values of the real and imaginary parts are combined by computing <code class="docutils literal notranslate"><span class="pre">hash(z.real)</span> <span class="pre">+</span> <span class="pre">sys.hash_info.imag</span> <span class="pre">*</span> <span class="pre">hash(z.imag)</span></code>, reduced modulo <code class="docutils literal notranslate"><span class="pre">2**sys.hash_info.width</span></code> so that it lies in <code class="docutils literal notranslate"><span class="pre">range(-2**(sys.hash_info.width</span> <span class="pre">-</span> <span class="pre">1),</span> <span class="pre">2**(sys.hash_info.width</span> <span class="pre">-</span> <span class="pre">1))</span></code>. Again, if the result is <code class="docutils literal notranslate"><span class="pre">-1</span></code>, it’s replaced with <code class="docutils literal notranslate"><span class="pre">-2</span></code>.</li> </ul> <p>To clarify the above rules, here’s some example Python code, equivalent to the built-in hash, for computing the hash of a rational number, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, or <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">sys</span><span class="o">,</span> <span class="nn">math</span> <span class="k">def</span> <span class="nf">hash_fraction</span><span class="p">(</span><span class="n">m</span><span class="p">,</span> <span class="n">n</span><span class="p">):</span> <span class="sd">"""Compute the hash of a rational number m / n.</span> <span class="sd"> Assumes m and n are integers, with n positive.</span> <span class="sd"> Equivalent to hash(fractions.Fraction(m, n)).</span> <span class="sd"> """</span> <span class="n">P</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">modulus</span> <span class="c1"># Remove common factors of P. (Unnecessary if m and n already coprime.)</span> <span class="k">while</span> <span class="n">m</span> <span class="o">%</span> <span class="n">P</span> <span class="o">==</span> <span class="n">n</span> <span class="o">%</span> <span class="n">P</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span> <span class="n">m</span><span class="p">,</span> <span class="n">n</span> <span class="o">=</span> <span class="n">m</span> <span class="o">//</span> <span class="n">P</span><span class="p">,</span> <span class="n">n</span> <span class="o">//</span> <span class="n">P</span> <span class="k">if</span> <span class="n">n</span> <span class="o">%</span> <span class="n">P</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">inf</span> <span class="k">else</span><span class="p">:</span> <span class="c1"># Fermat's Little Theorem: pow(n, P-1, P) is 1, so</span> <span class="c1"># pow(n, P-2, P) gives the inverse of n modulo P.</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="p">(</span><span class="nb">abs</span><span class="p">(</span><span class="n">m</span><span class="p">)</span> <span class="o">%</span> <span class="n">P</span><span class="p">)</span> <span class="o">*</span> <span class="nb">pow</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="n">P</span> <span class="o">-</span> <span class="mi">2</span><span class="p">,</span> <span class="n">P</span><span class="p">)</span> <span class="o">%</span> <span class="n">P</span> <span class="k">if</span> <span class="n">m</span> <span class="o"><</span> <span class="mi">0</span><span class="p">:</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="o">-</span><span class="n">hash_value</span> <span class="k">if</span> <span class="n">hash_value</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="p">:</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="o">-</span><span class="mi">2</span> <span class="k">return</span> <span class="n">hash_value</span> <span class="k">def</span> <span class="nf">hash_float</span><span class="p">(</span><span class="n">x</span><span class="p">):</span> <span class="sd">"""Compute the hash of a float x."""</span> <span class="k">if</span> <span class="n">math</span><span class="o">.</span><span class="n">isnan</span><span class="p">(</span><span class="n">x</span><span class="p">):</span> <span class="k">return</span> <span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">nan</span> <span class="k">elif</span> <span class="n">math</span><span class="o">.</span><span class="n">isinf</span><span class="p">(</span><span class="n">x</span><span class="p">):</span> <span class="k">return</span> <span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">inf</span> <span class="k">if</span> <span class="n">x</span> <span class="o">></span> <span class="mi">0</span> <span class="k">else</span> <span class="o">-</span><span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">inf</span> <span class="k">else</span><span class="p">:</span> <span class="k">return</span> <span class="n">hash_fraction</span><span class="p">(</span><span class="o">*</span><span class="n">x</span><span class="o">.</span><span class="n">as_integer_ratio</span><span class="p">())</span> <span class="k">def</span> <span class="nf">hash_complex</span><span class="p">(</span><span class="n">z</span><span class="p">):</span> <span class="sd">"""Compute the hash of a complex number z."""</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="n">hash_float</span><span class="p">(</span><span class="n">z</span><span class="o">.</span><span class="n">real</span><span class="p">)</span> <span class="o">+</span> <span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">imag</span> <span class="o">*</span> <span class="n">hash_float</span><span class="p">(</span><span class="n">z</span><span class="o">.</span><span class="n">imag</span><span class="p">)</span> <span class="c1"># do a signed reduction modulo 2**sys.hash_info.width</span> <span class="n">M</span> <span class="o">=</span> <span class="mi">2</span><span class="o">**</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">hash_info</span><span class="o">.</span><span class="n">width</span> <span class="o">-</span> <span class="mi">1</span><span class="p">)</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="p">(</span><span class="n">hash_value</span> <span class="o">&</span> <span class="p">(</span><span class="n">M</span> <span class="o">-</span> <span class="mi">1</span><span class="p">))</span> <span class="o">-</span> <span class="p">(</span><span class="n">hash_value</span> <span class="o">&</span> <span class="n">M</span><span class="p">)</span> <span class="k">if</span> <span class="n">hash_value</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="p">:</span> <span class="n">hash_value</span> <span class="o">=</span> <span class="o">-</span><span class="mi">2</span> <span class="k">return</span> <span class="n">hash_value</span> </pre></div> </div> </div> </div> <div class="section" id="iterator-types"> <span id="typeiter"></span><h2>4.5. Iterator Types<a class="headerlink" href="#iterator-types" title="Permalink to this headline">¶</a></h2> <p id="index-17">Python supports a concept of iteration over containers. This is implemented using two distinct methods; these are used to allow user-defined classes to support iteration. Sequences, described below in more detail, always support the iteration methods.</p> <p>One method needs to be defined for container objects to provide iteration support:</p> <dl class="method"> <dt id="container.__iter__"> <code class="descclassname">container.</code><code class="descname">__iter__</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#container.__iter__" title="Permalink to this definition">¶</a></dt> <dd><p>Return an iterator object. The object is required to support the iterator protocol described below. If a container supports different types of iteration, additional methods can be provided to specifically request iterators for those iteration types. (An example of an object supporting multiple forms of iteration would be a tree structure which supports both breadth-first and depth-first traversal.) This method corresponds to the <a class="reference internal" href="../c-api/typeobj.html#c.PyTypeObject.tp_iter" title="PyTypeObject.tp_iter"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_iter</span></code></a> slot of the type structure for Python objects in the Python/C API.</p> </dd></dl> <p>The iterator objects themselves are required to support the following two methods, which together form the <em class="dfn">iterator protocol</em>:</p> <dl class="method"> <dt id="iterator.__iter__"> <code class="descclassname">iterator.</code><code class="descname">__iter__</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#iterator.__iter__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the iterator object itself. This is required to allow both containers and iterators to be used with the <a class="reference internal" href="../reference/compound_stmts.html#for"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">for</span></code></a> and <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">in</span></code></a> statements. This method corresponds to the <a class="reference internal" href="../c-api/typeobj.html#c.PyTypeObject.tp_iter" title="PyTypeObject.tp_iter"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_iter</span></code></a> slot of the type structure for Python objects in the Python/C API.</p> </dd></dl> <dl class="method"> <dt id="iterator.__next__"> <code class="descclassname">iterator.</code><code class="descname">__next__</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#iterator.__next__" title="Permalink to this definition">¶</a></dt> <dd><p>Return the next item from the container. If there are no further items, raise the <a class="reference internal" href="exceptions.html#StopIteration" title="StopIteration"><code class="xref py py-exc docutils literal notranslate"><span class="pre">StopIteration</span></code></a> exception. This method corresponds to the <a class="reference internal" href="../c-api/typeobj.html#c.PyTypeObject.tp_iternext" title="PyTypeObject.tp_iternext"><code class="xref c c-member docutils literal notranslate"><span class="pre">tp_iternext</span></code></a> slot of the type structure for Python objects in the Python/C API.</p> </dd></dl> <p>Python defines several iterator objects to support iteration over general and specific sequence types, dictionaries, and other more specialized forms. The specific types are not important beyond their implementation of the iterator protocol.</p> <p>Once an iterator’s <a class="reference internal" href="#iterator.__next__" title="iterator.__next__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__next__()</span></code></a> method raises <a class="reference internal" href="exceptions.html#StopIteration" title="StopIteration"><code class="xref py py-exc docutils literal notranslate"><span class="pre">StopIteration</span></code></a>, it must continue to do so on subsequent calls. Implementations that do not obey this property are deemed broken.</p> <div class="section" id="generator-types"> <span id="id3"></span><h3>4.5.1. Generator Types<a class="headerlink" href="#generator-types" title="Permalink to this headline">¶</a></h3> <p>Python’s <a class="reference internal" href="../glossary.html#term-generator"><span class="xref std std-term">generator</span></a>s provide a convenient way to implement the iterator protocol. If a container object’s <a class="reference internal" href="../reference/datamodel.html#object.__iter__" title="object.__iter__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__iter__()</span></code></a> method is implemented as a generator, it will automatically return an iterator object (technically, a generator object) supplying the <a class="reference internal" href="../reference/datamodel.html#object.__iter__" title="object.__iter__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__iter__()</span></code></a> and <a class="reference internal" href="../reference/expressions.html#generator.__next__" title="generator.__next__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__next__()</span></code></a> methods. More information about generators can be found in <a class="reference internal" href="../reference/expressions.html#yieldexpr"><span class="std std-ref">the documentation for the yield expression</span></a>.</p> </div> </div> <div class="section" id="sequence-types-list-tuple-range"> <span id="typesseq"></span><h2>4.6. Sequence Types — <a class="reference internal" href="#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a>, <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a>, <a class="reference internal" href="#range" title="range"><code class="xref py py-class docutils literal notranslate"><span class="pre">range</span></code></a><a class="headerlink" href="#sequence-types-list-tuple-range" title="Permalink to this headline">¶</a></h2> <p>There are three basic sequence types: lists, tuples, and range objects. Additional sequence types tailored for processing of <a class="reference internal" href="#binaryseq"><span class="std std-ref">binary data</span></a> and <a class="reference internal" href="#textseq"><span class="std std-ref">text strings</span></a> are described in dedicated sections.</p> <div class="section" id="common-sequence-operations"> <span id="typesseq-common"></span><h3>4.6.1. Common Sequence Operations<a class="headerlink" href="#common-sequence-operations" title="Permalink to this headline">¶</a></h3> <p id="index-18">The operations in the following table are supported by most sequence types, both mutable and immutable. The <a class="reference internal" href="collections.abc.html#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.abc.Sequence</span></code></a> ABC is provided to make it easier to correctly implement these operations on custom sequence types.</p> <p>This table lists the sequence operations sorted in ascending priority. In the table, <em>s</em> and <em>t</em> are sequences of the same type, <em>n</em>, <em>i</em>, <em>j</em> and <em>k</em> are integers and <em>x</em> is an arbitrary object that meets any type and value restrictions imposed by <em>s</em>.</p> <p>The <code class="docutils literal notranslate"><span class="pre">in</span></code> and <code class="docutils literal notranslate"><span class="pre">not</span> <span class="pre">in</span></code> operations have the same priorities as the comparison operations. The <code class="docutils literal notranslate"><span class="pre">+</span></code> (concatenation) and <code class="docutils literal notranslate"><span class="pre">*</span></code> (repetition) operations have the same priority as the corresponding numeric operations. <a class="footnote-reference" href="#id14" id="id4">[3]</a></p> <table border="1" class="docutils" id="index-19"> <colgroup> <col width="38%" /> <col width="47%" /> <col width="15%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Result</th> <th class="head">Notes</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">in</span> <span class="pre">s</span></code></td> <td><code class="docutils literal notranslate"><span class="pre">True</span></code> if an item of <em>s</em> is equal to <em>x</em>, else <code class="docutils literal notranslate"><span class="pre">False</span></code></td> <td>(1)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">not</span> <span class="pre">in</span> <span class="pre">s</span></code></td> <td><code class="docutils literal notranslate"><span class="pre">False</span></code> if an item of <em>s</em> is equal to <em>x</em>, else <code class="docutils literal notranslate"><span class="pre">True</span></code></td> <td>(1)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s</span> <span class="pre">+</span> <span class="pre">t</span></code></td> <td>the concatenation of <em>s</em> and <em>t</em></td> <td>(6)(7)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s</span> <span class="pre">*</span> <span class="pre">n</span></code> or <code class="docutils literal notranslate"><span class="pre">n</span> <span class="pre">*</span> <span class="pre">s</span></code></td> <td>equivalent to adding <em>s</em> to itself <em>n</em> times</td> <td>(2)(7)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s[i]</span></code></td> <td><em>i</em>th item of <em>s</em>, origin 0</td> <td>(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s[i:j]</span></code></td> <td>slice of <em>s</em> from <em>i</em> to <em>j</em></td> <td>(3)(4)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s[i:j:k]</span></code></td> <td>slice of <em>s</em> from <em>i</em> to <em>j</em> with step <em>k</em></td> <td>(3)(5)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">len(s)</span></code></td> <td>length of <em>s</em></td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">min(s)</span></code></td> <td>smallest item of <em>s</em></td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">max(s)</span></code></td> <td>largest item of <em>s</em></td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s.index(x[,</span> <span class="pre">i[,</span> <span class="pre">j]])</span></code></td> <td>index of the first occurrence of <em>x</em> in <em>s</em> (at or after index <em>i</em> and before index <em>j</em>)</td> <td>(8)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s.count(x)</span></code></td> <td>total number of occurrences of <em>x</em> in <em>s</em></td> <td> </td> </tr> </tbody> </table> <p>Sequences of the same type also support comparisons. In particular, tuples and lists are compared lexicographically by comparing corresponding elements. This means that to compare equal, every element must compare equal and the two sequences must be of the same type and have the same length. (For full details see <a class="reference internal" href="../reference/expressions.html#comparisons"><span class="std std-ref">Comparisons</span></a> in the language reference.)</p> <p>Notes:</p> <ol class="arabic"> <li><p class="first">While the <code class="docutils literal notranslate"><span class="pre">in</span></code> and <code class="docutils literal notranslate"><span class="pre">not</span> <span class="pre">in</span></code> operations are used only for simple containment testing in the general case, some specialised sequences (such as <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a>, <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> and <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>) also use them for subsequence testing:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s2">"gg"</span> <span class="ow">in</span> <span class="s2">"eggs"</span> <span class="go">True</span> </pre></div> </div> </li> <li><p class="first">Values of <em>n</em> less than <code class="docutils literal notranslate"><span class="pre">0</span></code> are treated as <code class="docutils literal notranslate"><span class="pre">0</span></code> (which yields an empty sequence of the same type as <em>s</em>). Note that items in the sequence <em>s</em> are not copied; they are referenced multiple times. This often haunts new Python programmers; consider:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">lists</span> <span class="o">=</span> <span class="p">[[]]</span> <span class="o">*</span> <span class="mi">3</span> <span class="gp">>>> </span><span class="n">lists</span> <span class="go">[[], [], []]</span> <span class="gp">>>> </span><span class="n">lists</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">lists</span> <span class="go">[[3], [3], [3]]</span> </pre></div> </div> <p>What has happened is that <code class="docutils literal notranslate"><span class="pre">[[]]</span></code> is a one-element list containing an empty list, so all three elements of <code class="docutils literal notranslate"><span class="pre">[[]]</span> <span class="pre">*</span> <span class="pre">3</span></code> are references to this single empty list. Modifying any of the elements of <code class="docutils literal notranslate"><span class="pre">lists</span></code> modifies this single list. You can create a list of different lists this way:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">lists</span> <span class="o">=</span> <span class="p">[[]</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">3</span><span class="p">)]</span> <span class="gp">>>> </span><span class="n">lists</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">lists</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">lists</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">7</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">lists</span> <span class="go">[[3], [5], [7]]</span> </pre></div> </div> <p>Further explanation is available in the FAQ entry <a class="reference internal" href="../faq/programming.html#faq-multidimensional-list"><span class="std std-ref">How do I create a multidimensional list?</span></a>.</p> </li> <li><p class="first">If <em>i</em> or <em>j</em> is negative, the index is relative to the end of sequence <em>s</em>: <code class="docutils literal notranslate"><span class="pre">len(s)</span> <span class="pre">+</span> <span class="pre">i</span></code> or <code class="docutils literal notranslate"><span class="pre">len(s)</span> <span class="pre">+</span> <span class="pre">j</span></code> is substituted. But note that <code class="docutils literal notranslate"><span class="pre">-0</span></code> is still <code class="docutils literal notranslate"><span class="pre">0</span></code>.</p> </li> <li><p class="first">The slice of <em>s</em> from <em>i</em> to <em>j</em> is defined as the sequence of items with index <em>k</em> such that <code class="docutils literal notranslate"><span class="pre">i</span> <span class="pre"><=</span> <span class="pre">k</span> <span class="pre"><</span> <span class="pre">j</span></code>. If <em>i</em> or <em>j</em> is greater than <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>, use <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>. If <em>i</em> is omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, use <code class="docutils literal notranslate"><span class="pre">0</span></code>. If <em>j</em> is omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, use <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>. If <em>i</em> is greater than or equal to <em>j</em>, the slice is empty.</p> </li> <li><p class="first">The slice of <em>s</em> from <em>i</em> to <em>j</em> with step <em>k</em> is defined as the sequence of items with index <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">=</span> <span class="pre">i</span> <span class="pre">+</span> <span class="pre">n*k</span></code> such that <code class="docutils literal notranslate"><span class="pre">0</span> <span class="pre"><=</span> <span class="pre">n</span> <span class="pre"><</span> <span class="pre">(j-i)/k</span></code>. In other words, the indices are <code class="docutils literal notranslate"><span class="pre">i</span></code>, <code class="docutils literal notranslate"><span class="pre">i+k</span></code>, <code class="docutils literal notranslate"><span class="pre">i+2*k</span></code>, <code class="docutils literal notranslate"><span class="pre">i+3*k</span></code> and so on, stopping when <em>j</em> is reached (but never including <em>j</em>). When <em>k</em> is positive, <em>i</em> and <em>j</em> are reduced to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code> if they are greater. When <em>k</em> is negative, <em>i</em> and <em>j</em> are reduced to <code class="docutils literal notranslate"><span class="pre">len(s)</span> <span class="pre">-</span> <span class="pre">1</span></code> if they are greater. If <em>i</em> or <em>j</em> are omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, they become “end” values (which end depends on the sign of <em>k</em>). Note, <em>k</em> cannot be zero. If <em>k</em> is <code class="docutils literal notranslate"><span class="pre">None</span></code>, it is treated like <code class="docutils literal notranslate"><span class="pre">1</span></code>.</p> </li> <li><p class="first">Concatenating immutable sequences always results in a new object. This means that building up a sequence by repeated concatenation will have a quadratic runtime cost in the total sequence length. To get a linear runtime cost, you must switch to one of the alternatives below:</p> <ul class="simple"> <li>if concatenating <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> objects, you can build a list and use <a class="reference internal" href="#str.join" title="str.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.join()</span></code></a> at the end or else write to an <a class="reference internal" href="io.html#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.StringIO</span></code></a> instance and retrieve its value when complete</li> <li>if concatenating <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects, you can similarly use <a class="reference internal" href="#bytes.join" title="bytes.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytes.join()</span></code></a> or <a class="reference internal" href="io.html#io.BytesIO" title="io.BytesIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.BytesIO</span></code></a>, or you can do in-place concatenation with a <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> object. <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> objects are mutable and have an efficient overallocation mechanism</li> <li>if concatenating <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a> objects, extend a <a class="reference internal" href="#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a> instead</li> <li>for other types, investigate the relevant class documentation</li> </ul> </li> <li><p class="first">Some sequence types (such as <a class="reference internal" href="#range" title="range"><code class="xref py py-class docutils literal notranslate"><span class="pre">range</span></code></a>) only support item sequences that follow specific patterns, and hence don’t support sequence concatenation or repetition.</p> </li> <li><p class="first"><code class="docutils literal notranslate"><span class="pre">index</span></code> raises <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when <em>x</em> is not found in <em>s</em>. Not all implementations support passing the additional arguments <em>i</em> and <em>j</em>. These arguments allow efficient searching of subsections of the sequence. Passing the extra arguments is roughly equivalent to using <code class="docutils literal notranslate"><span class="pre">s[i:j].index(x)</span></code>, only without copying any data and with the returned index being relative to the start of the sequence rather than the start of the slice.</p> </li> </ol> </div> <div class="section" id="immutable-sequence-types"> <span id="typesseq-immutable"></span><h3>4.6.2. Immutable Sequence Types<a class="headerlink" href="#immutable-sequence-types" title="Permalink to this headline">¶</a></h3> <p id="index-20">The only operation that immutable sequence types generally implement that is not also implemented by mutable sequence types is support for the <a class="reference internal" href="functions.html#hash" title="hash"><code class="xref py py-func docutils literal notranslate"><span class="pre">hash()</span></code></a> built-in.</p> <p>This support allows immutable sequences, such as <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a> instances, to be used as <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> keys and stored in <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> and <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> instances.</p> <p>Attempting to hash an immutable sequence that contains unhashable values will result in <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> </div> <div class="section" id="mutable-sequence-types"> <span id="typesseq-mutable"></span><h3>4.6.3. Mutable Sequence Types<a class="headerlink" href="#mutable-sequence-types" title="Permalink to this headline">¶</a></h3> <p id="index-21">The operations in the following table are defined on mutable sequence types. The <a class="reference internal" href="collections.abc.html#collections.abc.MutableSequence" title="collections.abc.MutableSequence"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.abc.MutableSequence</span></code></a> ABC is provided to make it easier to correctly implement these operations on custom sequence types.</p> <p>In the table <em>s</em> is an instance of a mutable sequence type, <em>t</em> is any iterable object and <em>x</em> is an arbitrary object that meets any type and value restrictions imposed by <em>s</em> (for example, <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> only accepts integers that meet the value restriction <code class="docutils literal notranslate"><span class="pre">0</span> <span class="pre"><=</span> <span class="pre">x</span> <span class="pre"><=</span> <span class="pre">255</span></code>).</p> <table border="1" class="docutils" id="index-22"> <colgroup> <col width="36%" /> <col width="39%" /> <col width="25%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Operation</th> <th class="head">Result</th> <th class="head">Notes</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s[i]</span> <span class="pre">=</span> <span class="pre">x</span></code></td> <td>item <em>i</em> of <em>s</em> is replaced by <em>x</em></td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s[i:j]</span> <span class="pre">=</span> <span class="pre">t</span></code></td> <td>slice of <em>s</em> from <em>i</em> to <em>j</em> is replaced by the contents of the iterable <em>t</em></td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">del</span> <span class="pre">s[i:j]</span></code></td> <td>same as <code class="docutils literal notranslate"><span class="pre">s[i:j]</span> <span class="pre">=</span> <span class="pre">[]</span></code></td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s[i:j:k]</span> <span class="pre">=</span> <span class="pre">t</span></code></td> <td>the elements of <code class="docutils literal notranslate"><span class="pre">s[i:j:k]</span></code> are replaced by those of <em>t</em></td> <td>(1)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">del</span> <span class="pre">s[i:j:k]</span></code></td> <td>removes the elements of <code class="docutils literal notranslate"><span class="pre">s[i:j:k]</span></code> from the list</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s.append(x)</span></code></td> <td>appends <em>x</em> to the end of the sequence (same as <code class="docutils literal notranslate"><span class="pre">s[len(s):len(s)]</span> <span class="pre">=</span> <span class="pre">[x]</span></code>)</td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s.clear()</span></code></td> <td>removes all items from <em>s</em> (same as <code class="docutils literal notranslate"><span class="pre">del</span> <span class="pre">s[:]</span></code>)</td> <td>(5)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s.copy()</span></code></td> <td>creates a shallow copy of <em>s</em> (same as <code class="docutils literal notranslate"><span class="pre">s[:]</span></code>)</td> <td>(5)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s.extend(t)</span></code> or <code class="docutils literal notranslate"><span class="pre">s</span> <span class="pre">+=</span> <span class="pre">t</span></code></td> <td>extends <em>s</em> with the contents of <em>t</em> (for the most part the same as <code class="docutils literal notranslate"><span class="pre">s[len(s):len(s)]</span> <span class="pre">=</span> <span class="pre">t</span></code>)</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s</span> <span class="pre">*=</span> <span class="pre">n</span></code></td> <td>updates <em>s</em> with its contents repeated <em>n</em> times</td> <td>(6)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s.insert(i,</span> <span class="pre">x)</span></code></td> <td>inserts <em>x</em> into <em>s</em> at the index given by <em>i</em> (same as <code class="docutils literal notranslate"><span class="pre">s[i:i]</span> <span class="pre">=</span> <span class="pre">[x]</span></code>)</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s.pop([i])</span></code></td> <td>retrieves the item at <em>i</em> and also removes it from <em>s</em></td> <td>(2)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">s.remove(x)</span></code></td> <td>remove the first item from <em>s</em> where <code class="docutils literal notranslate"><span class="pre">s[i]</span> <span class="pre">==</span> <span class="pre">x</span></code></td> <td>(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">s.reverse()</span></code></td> <td>reverses the items of <em>s</em> in place</td> <td>(4)</td> </tr> </tbody> </table> <p>Notes:</p> <ol class="arabic"> <li><p class="first"><em>t</em> must have the same length as the slice it is replacing.</p> </li> <li><p class="first">The optional argument <em>i</em> defaults to <code class="docutils literal notranslate"><span class="pre">-1</span></code>, so that by default the last item is removed and returned.</p> </li> <li><p class="first"><code class="docutils literal notranslate"><span class="pre">remove</span></code> raises <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when <em>x</em> is not found in <em>s</em>.</p> </li> <li><p class="first">The <code class="xref py py-meth docutils literal notranslate"><span class="pre">reverse()</span></code> method modifies the sequence in place for economy of space when reversing a large sequence. To remind users that it operates by side effect, it does not return the reversed sequence.</p> </li> <li><p class="first"><code class="xref py py-meth docutils literal notranslate"><span class="pre">clear()</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">copy()</span></code> are included for consistency with the interfaces of mutable containers that don’t support slicing operations (such as <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> and <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a>)</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3: </span><code class="xref py py-meth docutils literal notranslate"><span class="pre">clear()</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">copy()</span></code> methods.</p> </div> </li> <li><p class="first">The value <em>n</em> is an integer, or an object implementing <a class="reference internal" href="../reference/datamodel.html#object.__index__" title="object.__index__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__index__()</span></code></a>. Zero and negative values of <em>n</em> clear the sequence. Items in the sequence are not copied; they are referenced multiple times, as explained for <code class="docutils literal notranslate"><span class="pre">s</span> <span class="pre">*</span> <span class="pre">n</span></code> under <a class="reference internal" href="#typesseq-common"><span class="std std-ref">Common Sequence Operations</span></a>.</p> </li> </ol> </div> <div class="section" id="lists"> <span id="typesseq-list"></span><h3>4.6.4. Lists<a class="headerlink" href="#lists" title="Permalink to this headline">¶</a></h3> <p id="index-23">Lists are mutable sequences, typically used to store collections of homogeneous items (where the precise degree of similarity will vary by application).</p> <dl class="class"> <dt id="list"> <em class="property">class </em><code class="descname">list</code><span class="sig-paren">(</span><span class="optional">[</span><em>iterable</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#list" title="Permalink to this definition">¶</a></dt> <dd><p>Lists may be constructed in several ways:</p> <ul class="simple"> <li>Using a pair of square brackets to denote the empty list: <code class="docutils literal notranslate"><span class="pre">[]</span></code></li> <li>Using square brackets, separating items with commas: <code class="docutils literal notranslate"><span class="pre">[a]</span></code>, <code class="docutils literal notranslate"><span class="pre">[a,</span> <span class="pre">b,</span> <span class="pre">c]</span></code></li> <li>Using a list comprehension: <code class="docutils literal notranslate"><span class="pre">[x</span> <span class="pre">for</span> <span class="pre">x</span> <span class="pre">in</span> <span class="pre">iterable]</span></code></li> <li>Using the type constructor: <code class="docutils literal notranslate"><span class="pre">list()</span></code> or <code class="docutils literal notranslate"><span class="pre">list(iterable)</span></code></li> </ul> <p>The constructor builds a list whose items are the same and in the same order as <em>iterable</em>’s items. <em>iterable</em> may be either a sequence, a container that supports iteration, or an iterator object. If <em>iterable</em> is already a list, a copy is made and returned, similar to <code class="docutils literal notranslate"><span class="pre">iterable[:]</span></code>. For example, <code class="docutils literal notranslate"><span class="pre">list('abc')</span></code> returns <code class="docutils literal notranslate"><span class="pre">['a',</span> <span class="pre">'b',</span> <span class="pre">'c']</span></code> and <code class="docutils literal notranslate"><span class="pre">list(</span> <span class="pre">(1,</span> <span class="pre">2,</span> <span class="pre">3)</span> <span class="pre">)</span></code> returns <code class="docutils literal notranslate"><span class="pre">[1,</span> <span class="pre">2,</span> <span class="pre">3]</span></code>. If no argument is given, the constructor creates a new empty list, <code class="docutils literal notranslate"><span class="pre">[]</span></code>.</p> <p>Many other operations also produce lists, including the <a class="reference internal" href="functions.html#sorted" title="sorted"><code class="xref py py-func docutils literal notranslate"><span class="pre">sorted()</span></code></a> built-in.</p> <p>Lists implement all of the <a class="reference internal" href="#typesseq-common"><span class="std std-ref">common</span></a> and <a class="reference internal" href="#typesseq-mutable"><span class="std std-ref">mutable</span></a> sequence operations. Lists also provide the following additional method:</p> <dl class="method"> <dt id="list.sort"> <code class="descname">sort</code><span class="sig-paren">(</span><em>*</em>, <em>key=None</em>, <em>reverse=False</em><span class="sig-paren">)</span><a class="headerlink" href="#list.sort" title="Permalink to this definition">¶</a></dt> <dd><p>This method sorts the list in place, using only <code class="docutils literal notranslate"><span class="pre"><</span></code> comparisons between items. Exceptions are not suppressed - if any comparison operations fail, the entire sort operation will fail (and the list will likely be left in a partially modified state).</p> <p><a class="reference internal" href="#list.sort" title="list.sort"><code class="xref py py-meth docutils literal notranslate"><span class="pre">sort()</span></code></a> accepts two arguments that can only be passed by keyword (<a class="reference internal" href="../glossary.html#keyword-only-parameter"><span class="std std-ref">keyword-only arguments</span></a>):</p> <p><em>key</em> specifies a function of one argument that is used to extract a comparison key from each list element (for example, <code class="docutils literal notranslate"><span class="pre">key=str.lower</span></code>). The key corresponding to each item in the list is calculated once and then used for the entire sorting process. The default value of <code class="docutils literal notranslate"><span class="pre">None</span></code> means that list items are sorted directly without calculating a separate key value.</p> <p>The <a class="reference internal" href="functools.html#functools.cmp_to_key" title="functools.cmp_to_key"><code class="xref py py-func docutils literal notranslate"><span class="pre">functools.cmp_to_key()</span></code></a> utility is available to convert a 2.x style <em>cmp</em> function to a <em>key</em> function.</p> <p><em>reverse</em> is a boolean value. If set to <code class="docutils literal notranslate"><span class="pre">True</span></code>, then the list elements are sorted as if each comparison were reversed.</p> <p>This method modifies the sequence in place for economy of space when sorting a large sequence. To remind users that it operates by side effect, it does not return the sorted sequence (use <a class="reference internal" href="functions.html#sorted" title="sorted"><code class="xref py py-func docutils literal notranslate"><span class="pre">sorted()</span></code></a> to explicitly request a new sorted list instance).</p> <p>The <a class="reference internal" href="#list.sort" title="list.sort"><code class="xref py py-meth docutils literal notranslate"><span class="pre">sort()</span></code></a> method is guaranteed to be stable. A sort is stable if it guarantees not to change the relative order of elements that compare equal — this is helpful for sorting in multiple passes (for example, sort by department, then by salary grade).</p> <div class="impl-detail compound"> <p><strong>CPython implementation detail:</strong> While a list is being sorted, the effect of attempting to mutate, or even inspect, the list is undefined. The C implementation of Python makes the list appear empty for the duration, and raises <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> if it can detect that the list has been mutated during a sort.</p> </div> </dd></dl> </dd></dl> </div> <div class="section" id="tuples"> <span id="typesseq-tuple"></span><h3>4.6.5. Tuples<a class="headerlink" href="#tuples" title="Permalink to this headline">¶</a></h3> <p id="index-24">Tuples are immutable sequences, typically used to store collections of heterogeneous data (such as the 2-tuples produced by the <a class="reference internal" href="functions.html#enumerate" title="enumerate"><code class="xref py py-func docutils literal notranslate"><span class="pre">enumerate()</span></code></a> built-in). Tuples are also used for cases where an immutable sequence of homogeneous data is needed (such as allowing storage in a <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> or <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> instance).</p> <dl class="class"> <dt id="tuple"> <em class="property">class </em><code class="descname">tuple</code><span class="sig-paren">(</span><span class="optional">[</span><em>iterable</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#tuple" title="Permalink to this definition">¶</a></dt> <dd><p>Tuples may be constructed in a number of ways:</p> <ul class="simple"> <li>Using a pair of parentheses to denote the empty tuple: <code class="docutils literal notranslate"><span class="pre">()</span></code></li> <li>Using a trailing comma for a singleton tuple: <code class="docutils literal notranslate"><span class="pre">a,</span></code> or <code class="docutils literal notranslate"><span class="pre">(a,)</span></code></li> <li>Separating items with commas: <code class="docutils literal notranslate"><span class="pre">a,</span> <span class="pre">b,</span> <span class="pre">c</span></code> or <code class="docutils literal notranslate"><span class="pre">(a,</span> <span class="pre">b,</span> <span class="pre">c)</span></code></li> <li>Using the <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-func docutils literal notranslate"><span class="pre">tuple()</span></code></a> built-in: <code class="docutils literal notranslate"><span class="pre">tuple()</span></code> or <code class="docutils literal notranslate"><span class="pre">tuple(iterable)</span></code></li> </ul> <p>The constructor builds a tuple whose items are the same and in the same order as <em>iterable</em>’s items. <em>iterable</em> may be either a sequence, a container that supports iteration, or an iterator object. If <em>iterable</em> is already a tuple, it is returned unchanged. For example, <code class="docutils literal notranslate"><span class="pre">tuple('abc')</span></code> returns <code class="docutils literal notranslate"><span class="pre">('a',</span> <span class="pre">'b',</span> <span class="pre">'c')</span></code> and <code class="docutils literal notranslate"><span class="pre">tuple(</span> <span class="pre">[1,</span> <span class="pre">2,</span> <span class="pre">3]</span> <span class="pre">)</span></code> returns <code class="docutils literal notranslate"><span class="pre">(1,</span> <span class="pre">2,</span> <span class="pre">3)</span></code>. If no argument is given, the constructor creates a new empty tuple, <code class="docutils literal notranslate"><span class="pre">()</span></code>.</p> <p>Note that it is actually the comma which makes a tuple, not the parentheses. The parentheses are optional, except in the empty tuple case, or when they are needed to avoid syntactic ambiguity. For example, <code class="docutils literal notranslate"><span class="pre">f(a,</span> <span class="pre">b,</span> <span class="pre">c)</span></code> is a function call with three arguments, while <code class="docutils literal notranslate"><span class="pre">f((a,</span> <span class="pre">b,</span> <span class="pre">c))</span></code> is a function call with a 3-tuple as the sole argument.</p> <p>Tuples implement all of the <a class="reference internal" href="#typesseq-common"><span class="std std-ref">common</span></a> sequence operations.</p> </dd></dl> <p>For heterogeneous collections of data where access by name is clearer than access by index, <a class="reference internal" href="collections.html#collections.namedtuple" title="collections.namedtuple"><code class="xref py py-func docutils literal notranslate"><span class="pre">collections.namedtuple()</span></code></a> may be a more appropriate choice than a simple tuple object.</p> </div> <div class="section" id="ranges"> <span id="typesseq-range"></span><h3>4.6.6. Ranges<a class="headerlink" href="#ranges" title="Permalink to this headline">¶</a></h3> <p id="index-25">The <a class="reference internal" href="#range" title="range"><code class="xref py py-class docutils literal notranslate"><span class="pre">range</span></code></a> type represents an immutable sequence of numbers and is commonly used for looping a specific number of times in <a class="reference internal" href="../reference/compound_stmts.html#for"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">for</span></code></a> loops.</p> <dl class="class"> <dt id="range"> <em class="property">class </em><code class="descname">range</code><span class="sig-paren">(</span><em>stop</em><span class="sig-paren">)</span><a class="headerlink" href="#range" title="Permalink to this definition">¶</a></dt> <dt> <em class="property">class </em><code class="descname">range</code><span class="sig-paren">(</span><em>start</em>, <em>stop</em><span class="optional">[</span>, <em>step</em><span class="optional">]</span><span class="sig-paren">)</span></dt> <dd><p>The arguments to the range constructor must be integers (either built-in <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a> or any object that implements the <code class="docutils literal notranslate"><span class="pre">__index__</span></code> special method). If the <em>step</em> argument is omitted, it defaults to <code class="docutils literal notranslate"><span class="pre">1</span></code>. If the <em>start</em> argument is omitted, it defaults to <code class="docutils literal notranslate"><span class="pre">0</span></code>. If <em>step</em> is zero, <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> is raised.</p> <p>For a positive <em>step</em>, the contents of a range <code class="docutils literal notranslate"><span class="pre">r</span></code> are determined by the formula <code class="docutils literal notranslate"><span class="pre">r[i]</span> <span class="pre">=</span> <span class="pre">start</span> <span class="pre">+</span> <span class="pre">step*i</span></code> where <code class="docutils literal notranslate"><span class="pre">i</span> <span class="pre">>=</span> <span class="pre">0</span></code> and <code class="docutils literal notranslate"><span class="pre">r[i]</span> <span class="pre"><</span> <span class="pre">stop</span></code>.</p> <p>For a negative <em>step</em>, the contents of the range are still determined by the formula <code class="docutils literal notranslate"><span class="pre">r[i]</span> <span class="pre">=</span> <span class="pre">start</span> <span class="pre">+</span> <span class="pre">step*i</span></code>, but the constraints are <code class="docutils literal notranslate"><span class="pre">i</span> <span class="pre">>=</span> <span class="pre">0</span></code> and <code class="docutils literal notranslate"><span class="pre">r[i]</span> <span class="pre">></span> <span class="pre">stop</span></code>.</p> <p>A range object will be empty if <code class="docutils literal notranslate"><span class="pre">r[0]</span></code> does not meet the value constraint. Ranges do support negative indices, but these are interpreted as indexing from the end of the sequence determined by the positive indices.</p> <p>Ranges containing absolute values larger than <a class="reference internal" href="sys.html#sys.maxsize" title="sys.maxsize"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.maxsize</span></code></a> are permitted but some features (such as <a class="reference internal" href="functions.html#len" title="len"><code class="xref py py-func docutils literal notranslate"><span class="pre">len()</span></code></a>) may raise <a class="reference internal" href="exceptions.html#OverflowError" title="OverflowError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OverflowError</span></code></a>.</p> <p>Range examples:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">))</span> <span class="go">[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">11</span><span class="p">))</span> <span class="go">[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">30</span><span class="p">,</span> <span class="mi">5</span><span class="p">))</span> <span class="go">[0, 5, 10, 15, 20, 25]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">3</span><span class="p">))</span> <span class="go">[0, 3, 6, 9]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="o">-</span><span class="mi">10</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">))</span> <span class="go">[0, -1, -2, -3, -4, -5, -6, -7, -8, -9]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">))</span> <span class="go">[]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">0</span><span class="p">))</span> <span class="go">[]</span> </pre></div> </div> <p>Ranges implement all of the <a class="reference internal" href="#typesseq-common"><span class="std std-ref">common</span></a> sequence operations except concatenation and repetition (due to the fact that range objects can only represent sequences that follow a strict pattern and repetition and concatenation will usually violate that pattern).</p> <dl class="attribute"> <dt id="range.start"> <code class="descname">start</code><a class="headerlink" href="#range.start" title="Permalink to this definition">¶</a></dt> <dd><p>The value of the <em>start</em> parameter (or <code class="docutils literal notranslate"><span class="pre">0</span></code> if the parameter was not supplied)</p> </dd></dl> <dl class="attribute"> <dt id="range.stop"> <code class="descname">stop</code><a class="headerlink" href="#range.stop" title="Permalink to this definition">¶</a></dt> <dd><p>The value of the <em>stop</em> parameter</p> </dd></dl> <dl class="attribute"> <dt id="range.step"> <code class="descname">step</code><a class="headerlink" href="#range.step" title="Permalink to this definition">¶</a></dt> <dd><p>The value of the <em>step</em> parameter (or <code class="docutils literal notranslate"><span class="pre">1</span></code> if the parameter was not supplied)</p> </dd></dl> </dd></dl> <p>The advantage of the <a class="reference internal" href="#range" title="range"><code class="xref py py-class docutils literal notranslate"><span class="pre">range</span></code></a> type over a regular <a class="reference internal" href="#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a> or <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a> is that a <a class="reference internal" href="#range" title="range"><code class="xref py py-class docutils literal notranslate"><span class="pre">range</span></code></a> object will always take the same (small) amount of memory, no matter the size of the range it represents (as it only stores the <code class="docutils literal notranslate"><span class="pre">start</span></code>, <code class="docutils literal notranslate"><span class="pre">stop</span></code> and <code class="docutils literal notranslate"><span class="pre">step</span></code> values, calculating individual items and subranges as needed).</p> <p>Range objects implement the <a class="reference internal" href="collections.abc.html#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.abc.Sequence</span></code></a> ABC, and provide features such as containment tests, element index lookup, slicing and support for negative indices (see <a class="reference internal" href="#typesseq"><span class="std std-ref">Sequence Types — list, tuple, range</span></a>):</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">r</span> <span class="o">=</span> <span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">20</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">r</span> <span class="go">range(0, 20, 2)</span> <span class="gp">>>> </span><span class="mi">11</span> <span class="ow">in</span> <span class="n">r</span> <span class="go">False</span> <span class="gp">>>> </span><span class="mi">10</span> <span class="ow">in</span> <span class="n">r</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">r</span><span class="o">.</span><span class="n">index</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span> <span class="go">5</span> <span class="gp">>>> </span><span class="n">r</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span> <span class="go">10</span> <span class="gp">>>> </span><span class="n">r</span><span class="p">[:</span><span class="mi">5</span><span class="p">]</span> <span class="go">range(0, 10, 2)</span> <span class="gp">>>> </span><span class="n">r</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="go">18</span> </pre></div> </div> <p>Testing range objects for equality with <code class="docutils literal notranslate"><span class="pre">==</span></code> and <code class="docutils literal notranslate"><span class="pre">!=</span></code> compares them as sequences. That is, two range objects are considered equal if they represent the same sequence of values. (Note that two range objects that compare equal might have different <a class="reference internal" href="#range.start" title="range.start"><code class="xref py py-attr docutils literal notranslate"><span class="pre">start</span></code></a>, <a class="reference internal" href="#range.stop" title="range.stop"><code class="xref py py-attr docutils literal notranslate"><span class="pre">stop</span></code></a> and <a class="reference internal" href="#range.step" title="range.step"><code class="xref py py-attr docutils literal notranslate"><span class="pre">step</span></code></a> attributes, for example <code class="docutils literal notranslate"><span class="pre">range(0)</span> <span class="pre">==</span> <span class="pre">range(2,</span> <span class="pre">1,</span> <span class="pre">3)</span></code> or <code class="docutils literal notranslate"><span class="pre">range(0,</span> <span class="pre">3,</span> <span class="pre">2)</span> <span class="pre">==</span> <span class="pre">range(0,</span> <span class="pre">4,</span> <span class="pre">2)</span></code>.)</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span>Implement the Sequence ABC. Support slicing and negative indices. Test <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a> objects for membership in constant time instead of iterating through all items.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Define ‘==’ and ‘!=’ to compare range objects based on the sequence of values they define (instead of comparing based on object identity).</p> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3: </span>The <a class="reference internal" href="#range.start" title="range.start"><code class="xref py py-attr docutils literal notranslate"><span class="pre">start</span></code></a>, <a class="reference internal" href="#range.stop" title="range.stop"><code class="xref py py-attr docutils literal notranslate"><span class="pre">stop</span></code></a> and <a class="reference internal" href="#range.step" title="range.step"><code class="xref py py-attr docutils literal notranslate"><span class="pre">step</span></code></a> attributes.</p> </div> <div class="admonition seealso"> <p class="first admonition-title">See also</p> <ul class="last simple"> <li>The <a class="reference external" href="http://code.activestate.com/recipes/579000/">linspace recipe</a> shows how to implement a lazy version of range suitable for floating point applications.</li> </ul> </div> </div> </div> <div class="section" id="text-sequence-type-str"> <span id="textseq"></span><span id="index-26"></span><h2>4.7. Text Sequence Type — <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a><a class="headerlink" href="#text-sequence-type-str" title="Permalink to this headline">¶</a></h2> <p>Textual data in Python is handled with <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> objects, or <em class="dfn">strings</em>. Strings are immutable <a class="reference internal" href="#typesseq"><span class="std std-ref">sequences</span></a> of Unicode code points. String literals are written in a variety of ways:</p> <ul class="simple"> <li>Single quotes: <code class="docutils literal notranslate"><span class="pre">'allows</span> <span class="pre">embedded</span> <span class="pre">"double"</span> <span class="pre">quotes'</span></code></li> <li>Double quotes: <code class="docutils literal notranslate"><span class="pre">"allows</span> <span class="pre">embedded</span> <span class="pre">'single'</span> <span class="pre">quotes"</span></code>.</li> <li>Triple quoted: <code class="docutils literal notranslate"><span class="pre">'''Three</span> <span class="pre">single</span> <span class="pre">quotes'''</span></code>, <code class="docutils literal notranslate"><span class="pre">"""Three</span> <span class="pre">double</span> <span class="pre">quotes"""</span></code></li> </ul> <p>Triple quoted strings may span multiple lines - all associated whitespace will be included in the string literal.</p> <p>String literals that are part of a single expression and have only whitespace between them will be implicitly converted to a single string literal. That is, <code class="docutils literal notranslate"><span class="pre">("spam</span> <span class="pre">"</span> <span class="pre">"eggs")</span> <span class="pre">==</span> <span class="pre">"spam</span> <span class="pre">eggs"</span></code>.</p> <p>See <a class="reference internal" href="../reference/lexical_analysis.html#strings"><span class="std std-ref">String and Bytes literals</span></a> for more about the various forms of string literal, including supported escape sequences, and the <code class="docutils literal notranslate"><span class="pre">r</span></code> (“raw”) prefix that disables most escape sequence processing.</p> <p>Strings may also be created from other objects using the <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> constructor.</p> <p>Since there is no separate “character” type, indexing a string produces strings of length 1. That is, for a non-empty string <em>s</em>, <code class="docutils literal notranslate"><span class="pre">s[0]</span> <span class="pre">==</span> <span class="pre">s[0:1]</span></code>.</p> <p id="index-27">There is also no mutable string type, but <a class="reference internal" href="#str.join" title="str.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.join()</span></code></a> or <a class="reference internal" href="io.html#io.StringIO" title="io.StringIO"><code class="xref py py-class docutils literal notranslate"><span class="pre">io.StringIO</span></code></a> can be used to efficiently construct strings from multiple fragments.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>For backwards compatibility with the Python 2 series, the <code class="docutils literal notranslate"><span class="pre">u</span></code> prefix is once again permitted on string literals. It has no effect on the meaning of string literals and cannot be combined with the <code class="docutils literal notranslate"><span class="pre">r</span></code> prefix.</p> </div> <span class="target" id="index-28"></span><dl class="class"> <dt id="str"> <em class="property">class </em><code class="descname">str</code><span class="sig-paren">(</span><em>object=''</em><span class="sig-paren">)</span><a class="headerlink" href="#str" title="Permalink to this definition">¶</a></dt> <dt> <em class="property">class </em><code class="descname">str</code><span class="sig-paren">(</span><em>object=b''</em>, <em>encoding='utf-8'</em>, <em>errors='strict'</em><span class="sig-paren">)</span></dt> <dd><p>Return a <a class="reference internal" href="#textseq"><span class="std std-ref">string</span></a> version of <em>object</em>. If <em>object</em> is not provided, returns the empty string. Otherwise, the behavior of <code class="docutils literal notranslate"><span class="pre">str()</span></code> depends on whether <em>encoding</em> or <em>errors</em> is given, as follows.</p> <p>If neither <em>encoding</em> nor <em>errors</em> is given, <code class="docutils literal notranslate"><span class="pre">str(object)</span></code> returns <a class="reference internal" href="../reference/datamodel.html#object.__str__" title="object.__str__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">object.__str__()</span></code></a>, which is the “informal” or nicely printable string representation of <em>object</em>. For string objects, this is the string itself. If <em>object</em> does not have a <a class="reference internal" href="../reference/datamodel.html#object.__str__" title="object.__str__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__str__()</span></code></a> method, then <a class="reference internal" href="#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> falls back to returning <a class="reference internal" href="functions.html#repr" title="repr"><code class="xref py py-meth docutils literal notranslate"><span class="pre">repr(object)</span></code></a>.</p> <p id="index-29">If at least one of <em>encoding</em> or <em>errors</em> is given, <em>object</em> should be a <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> (e.g. <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> or <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>). In this case, if <em>object</em> is a <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> (or <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>) object, then <code class="docutils literal notranslate"><span class="pre">str(bytes,</span> <span class="pre">encoding,</span> <span class="pre">errors)</span></code> is equivalent to <a class="reference internal" href="#bytes.decode" title="bytes.decode"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytes.decode(encoding,</span> <span class="pre">errors)</span></code></a>. Otherwise, the bytes object underlying the buffer object is obtained before calling <a class="reference internal" href="#bytes.decode" title="bytes.decode"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytes.decode()</span></code></a>. See <a class="reference internal" href="#binaryseq"><span class="std std-ref">Binary Sequence Types — bytes, bytearray, memoryview</span></a> and <a class="reference internal" href="../c-api/buffer.html#bufferobjects"><span class="std std-ref">Buffer Protocol</span></a> for information on buffer objects.</p> <p>Passing a <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> object to <a class="reference internal" href="#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> without the <em>encoding</em> or <em>errors</em> arguments falls under the first case of returning the informal string representation (see also the <a class="reference internal" href="../using/cmdline.html#cmdoption-b"><code class="xref std std-option docutils literal notranslate"><span class="pre">-b</span></code></a> command-line option to Python). For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">str</span><span class="p">(</span><span class="sa">b</span><span class="s1">'Zoot!'</span><span class="p">)</span> <span class="go">"b'Zoot!'"</span> </pre></div> </div> <p>For more information on the <code class="docutils literal notranslate"><span class="pre">str</span></code> class and its methods, see <a class="reference internal" href="#textseq"><span class="std std-ref">Text Sequence Type — str</span></a> and the <a class="reference internal" href="#string-methods"><span class="std std-ref">String Methods</span></a> section below. To output formatted strings, see the <a class="reference internal" href="../reference/lexical_analysis.html#f-strings"><span class="std std-ref">Formatted string literals</span></a> and <a class="reference internal" href="string.html#formatstrings"><span class="std std-ref">Format String Syntax</span></a> sections. In addition, see the <a class="reference internal" href="text.html#stringservices"><span class="std std-ref">Text Processing Services</span></a> section.</p> </dd></dl> <div class="section" id="string-methods"> <span id="index-30"></span><span id="id5"></span><h3>4.7.1. String Methods<a class="headerlink" href="#string-methods" title="Permalink to this headline">¶</a></h3> <p id="index-31">Strings implement all of the <a class="reference internal" href="#typesseq-common"><span class="std std-ref">common</span></a> sequence operations, along with the additional methods described below.</p> <p>Strings also support two styles of string formatting, one providing a large degree of flexibility and customization (see <a class="reference internal" href="#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a>, <a class="reference internal" href="string.html#formatstrings"><span class="std std-ref">Format String Syntax</span></a> and <a class="reference internal" href="string.html#string-formatting"><span class="std std-ref">Custom String Formatting</span></a>) and the other based on C <code class="docutils literal notranslate"><span class="pre">printf</span></code> style formatting that handles a narrower range of types and is slightly harder to use correctly, but is often faster for the cases it can handle (<a class="reference internal" href="#old-string-formatting"><span class="std std-ref">printf-style String Formatting</span></a>).</p> <p>The <a class="reference internal" href="text.html#textservices"><span class="std std-ref">Text Processing Services</span></a> section of the standard library covers a number of other modules that provide various text related utilities (including regular expression support in the <a class="reference internal" href="re.html#module-re" title="re: Regular expression operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">re</span></code></a> module).</p> <dl class="method"> <dt id="str.capitalize"> <code class="descclassname">str.</code><code class="descname">capitalize</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.capitalize" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with its first character capitalized and the rest lowercased.</p> </dd></dl> <dl class="method"> <dt id="str.casefold"> <code class="descclassname">str.</code><code class="descname">casefold</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.casefold" title="Permalink to this definition">¶</a></dt> <dd><p>Return a casefolded copy of the string. Casefolded strings may be used for caseless matching.</p> <p>Casefolding is similar to lowercasing but more aggressive because it is intended to remove all case distinctions in a string. For example, the German lowercase letter <code class="docutils literal notranslate"><span class="pre">'ß'</span></code> is equivalent to <code class="docutils literal notranslate"><span class="pre">"ss"</span></code>. Since it is already lowercase, <a class="reference internal" href="#str.lower" title="str.lower"><code class="xref py py-meth docutils literal notranslate"><span class="pre">lower()</span></code></a> would do nothing to <code class="docutils literal notranslate"><span class="pre">'ß'</span></code>; <a class="reference internal" href="#str.casefold" title="str.casefold"><code class="xref py py-meth docutils literal notranslate"><span class="pre">casefold()</span></code></a> converts it to <code class="docutils literal notranslate"><span class="pre">"ss"</span></code>.</p> <p>The casefolding algorithm is described in section 3.13 of the Unicode Standard.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="method"> <dt id="str.center"> <code class="descclassname">str.</code><code class="descname">center</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillchar</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.center" title="Permalink to this definition">¶</a></dt> <dd><p>Return centered in a string of length <em>width</em>. Padding is done using the specified <em>fillchar</em> (default is an ASCII space). The original string is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> </dd></dl> <dl class="method"> <dt id="str.count"> <code class="descclassname">str.</code><code class="descname">count</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.count" title="Permalink to this definition">¶</a></dt> <dd><p>Return the number of non-overlapping occurrences of substring <em>sub</em> in the range [<em>start</em>, <em>end</em>]. Optional arguments <em>start</em> and <em>end</em> are interpreted as in slice notation.</p> </dd></dl> <dl class="method"> <dt id="str.encode"> <code class="descclassname">str.</code><code class="descname">encode</code><span class="sig-paren">(</span><em>encoding="utf-8"</em>, <em>errors="strict"</em><span class="sig-paren">)</span><a class="headerlink" href="#str.encode" title="Permalink to this definition">¶</a></dt> <dd><p>Return an encoded version of the string as a bytes object. Default encoding is <code class="docutils literal notranslate"><span class="pre">'utf-8'</span></code>. <em>errors</em> may be given to set a different error handling scheme. The default for <em>errors</em> is <code class="docutils literal notranslate"><span class="pre">'strict'</span></code>, meaning that encoding errors raise a <a class="reference internal" href="exceptions.html#UnicodeError" title="UnicodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">UnicodeError</span></code></a>. Other possible values are <code class="docutils literal notranslate"><span class="pre">'ignore'</span></code>, <code class="docutils literal notranslate"><span class="pre">'replace'</span></code>, <code class="docutils literal notranslate"><span class="pre">'xmlcharrefreplace'</span></code>, <code class="docutils literal notranslate"><span class="pre">'backslashreplace'</span></code> and any other name registered via <a class="reference internal" href="codecs.html#codecs.register_error" title="codecs.register_error"><code class="xref py py-func docutils literal notranslate"><span class="pre">codecs.register_error()</span></code></a>, see section <a class="reference internal" href="codecs.html#error-handlers"><span class="std std-ref">Error Handlers</span></a>. For a list of possible encodings, see section <a class="reference internal" href="codecs.html#standard-encodings"><span class="std std-ref">Standard Encodings</span></a>.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.1: </span>Support for keyword arguments added.</p> </div> </dd></dl> <dl class="method"> <dt id="str.endswith"> <code class="descclassname">str.</code><code class="descname">endswith</code><span class="sig-paren">(</span><em>suffix</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.endswith" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the string ends with the specified <em>suffix</em>, otherwise return <code class="docutils literal notranslate"><span class="pre">False</span></code>. <em>suffix</em> can also be a tuple of suffixes to look for. With optional <em>start</em>, test beginning at that position. With optional <em>end</em>, stop comparing at that position.</p> </dd></dl> <dl class="method"> <dt id="str.expandtabs"> <code class="descclassname">str.</code><code class="descname">expandtabs</code><span class="sig-paren">(</span><em>tabsize=8</em><span class="sig-paren">)</span><a class="headerlink" href="#str.expandtabs" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string where all tab characters are replaced by one or more spaces, depending on the current column and the given tab size. Tab positions occur every <em>tabsize</em> characters (default is 8, giving tab positions at columns 0, 8, 16 and so on). To expand the string, the current column is set to zero and the string is examined character by character. If the character is a tab (<code class="docutils literal notranslate"><span class="pre">\t</span></code>), one or more space characters are inserted in the result until the current column is equal to the next tab position. (The tab character itself is not copied.) If the character is a newline (<code class="docutils literal notranslate"><span class="pre">\n</span></code>) or return (<code class="docutils literal notranslate"><span class="pre">\r</span></code>), it is copied and the current column is reset to zero. Any other character is copied unchanged and the current column is incremented by one regardless of how the character is represented when printed.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'01</span><span class="se">\t</span><span class="s1">012</span><span class="se">\t</span><span class="s1">0123</span><span class="se">\t</span><span class="s1">01234'</span><span class="o">.</span><span class="n">expandtabs</span><span class="p">()</span> <span class="go">'01 012 0123 01234'</span> <span class="gp">>>> </span><span class="s1">'01</span><span class="se">\t</span><span class="s1">012</span><span class="se">\t</span><span class="s1">0123</span><span class="se">\t</span><span class="s1">01234'</span><span class="o">.</span><span class="n">expandtabs</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="go">'01 012 0123 01234'</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="str.find"> <code class="descclassname">str.</code><code class="descname">find</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.find" title="Permalink to this definition">¶</a></dt> <dd><p>Return the lowest index in the string where substring <em>sub</em> is found within the slice <code class="docutils literal notranslate"><span class="pre">s[start:end]</span></code>. Optional arguments <em>start</em> and <em>end</em> are interpreted as in slice notation. Return <code class="docutils literal notranslate"><span class="pre">-1</span></code> if <em>sub</em> is not found.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p>The <a class="reference internal" href="#str.find" title="str.find"><code class="xref py py-meth docutils literal notranslate"><span class="pre">find()</span></code></a> method should be used only if you need to know the position of <em>sub</em>. To check if <em>sub</em> is a substring or not, use the <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">in</span></code></a> operator:</p> <div class="last highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'Py'</span> <span class="ow">in</span> <span class="s1">'Python'</span> <span class="go">True</span> </pre></div> </div> </div> </dd></dl> <dl class="method"> <dt id="str.format"> <code class="descclassname">str.</code><code class="descname">format</code><span class="sig-paren">(</span><em>*args</em>, <em>**kwargs</em><span class="sig-paren">)</span><a class="headerlink" href="#str.format" title="Permalink to this definition">¶</a></dt> <dd><p>Perform a string formatting operation. The string on which this method is called can contain literal text or replacement fields delimited by braces <code class="docutils literal notranslate"><span class="pre">{}</span></code>. Each replacement field contains either the numeric index of a positional argument, or the name of a keyword argument. Returns a copy of the string where each replacement field is replaced with the string value of the corresponding argument.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s2">"The sum of 1 + 2 is </span><span class="si">{0}</span><span class="s2">"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="mi">1</span><span class="o">+</span><span class="mi">2</span><span class="p">)</span> <span class="go">'The sum of 1 + 2 is 3'</span> </pre></div> </div> <p>See <a class="reference internal" href="string.html#formatstrings"><span class="std std-ref">Format String Syntax</span></a> for a description of the various formatting options that can be specified in format strings.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">When formatting a number (<a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-class docutils literal notranslate"><span class="pre">int</span></code></a>, <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-class docutils literal notranslate"><span class="pre">float</span></code></a>, <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-class docutils literal notranslate"><span class="pre">complex</span></code></a>, <a class="reference internal" href="decimal.html#decimal.Decimal" title="decimal.Decimal"><code class="xref py py-class docutils literal notranslate"><span class="pre">decimal.Decimal</span></code></a> and subclasses) with the <code class="docutils literal notranslate"><span class="pre">n</span></code> type (ex: <code class="docutils literal notranslate"><span class="pre">'{:n}'.format(1234)</span></code>), the function temporarily sets the <code class="docutils literal notranslate"><span class="pre">LC_CTYPE</span></code> locale to the <code class="docutils literal notranslate"><span class="pre">LC_NUMERIC</span></code> locale to decode <code class="docutils literal notranslate"><span class="pre">decimal_point</span></code> and <code class="docutils literal notranslate"><span class="pre">thousands_sep</span></code> fields of <code class="xref c c-func docutils literal notranslate"><span class="pre">localeconv()</span></code> if they are non-ASCII or longer than 1 byte, and the <code class="docutils literal notranslate"><span class="pre">LC_NUMERIC</span></code> locale is different than the <code class="docutils literal notranslate"><span class="pre">LC_CTYPE</span></code> locale. This temporary change affects other threads.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6.5: </span>When formatting a number with the <code class="docutils literal notranslate"><span class="pre">n</span></code> type, the function sets temporarily the <code class="docutils literal notranslate"><span class="pre">LC_CTYPE</span></code> locale to the <code class="docutils literal notranslate"><span class="pre">LC_NUMERIC</span></code> locale in some cases.</p> </div> </dd></dl> <dl class="method"> <dt id="str.format_map"> <code class="descclassname">str.</code><code class="descname">format_map</code><span class="sig-paren">(</span><em>mapping</em><span class="sig-paren">)</span><a class="headerlink" href="#str.format_map" title="Permalink to this definition">¶</a></dt> <dd><p>Similar to <code class="docutils literal notranslate"><span class="pre">str.format(**mapping)</span></code>, except that <code class="docutils literal notranslate"><span class="pre">mapping</span></code> is used directly and not copied to a <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>. This is useful if for example <code class="docutils literal notranslate"><span class="pre">mapping</span></code> is a dict subclass:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">class</span> <span class="nc">Default</span><span class="p">(</span><span class="nb">dict</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">__missing__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">):</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">key</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="s1">'</span><span class="si">{name}</span><span class="s1"> was born in </span><span class="si">{country}</span><span class="s1">'</span><span class="o">.</span><span class="n">format_map</span><span class="p">(</span><span class="n">Default</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s1">'Guido'</span><span class="p">))</span> <span class="go">'Guido was born in country'</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.2.</span></p> </div> </dd></dl> <dl class="method"> <dt id="str.index"> <code class="descclassname">str.</code><code class="descname">index</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.index" title="Permalink to this definition">¶</a></dt> <dd><p>Like <a class="reference internal" href="#str.find" title="str.find"><code class="xref py py-meth docutils literal notranslate"><span class="pre">find()</span></code></a>, but raise <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when the substring is not found.</p> </dd></dl> <dl class="method"> <dt id="str.isalnum"> <code class="descclassname">str.</code><code class="descname">isalnum</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isalnum" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all characters in the string are alphanumeric and there is at least one character, false otherwise. A character <code class="docutils literal notranslate"><span class="pre">c</span></code> is alphanumeric if one of the following returns <code class="docutils literal notranslate"><span class="pre">True</span></code>: <code class="docutils literal notranslate"><span class="pre">c.isalpha()</span></code>, <code class="docutils literal notranslate"><span class="pre">c.isdecimal()</span></code>, <code class="docutils literal notranslate"><span class="pre">c.isdigit()</span></code>, or <code class="docutils literal notranslate"><span class="pre">c.isnumeric()</span></code>.</p> </dd></dl> <dl class="method"> <dt id="str.isalpha"> <code class="descclassname">str.</code><code class="descname">isalpha</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isalpha" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all characters in the string are alphabetic and there is at least one character, false otherwise. Alphabetic characters are those characters defined in the Unicode character database as “Letter”, i.e., those with general category property being one of “Lm”, “Lt”, “Lu”, “Ll”, or “Lo”. Note that this is different from the “Alphabetic” property defined in the Unicode Standard.</p> </dd></dl> <dl class="method"> <dt id="str.isdecimal"> <code class="descclassname">str.</code><code class="descname">isdecimal</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isdecimal" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all characters in the string are decimal characters and there is at least one character, false otherwise. Decimal characters are those that can be used to form numbers in base 10, e.g. U+0660, ARABIC-INDIC DIGIT ZERO. Formally a decimal character is a character in the Unicode General Category “Nd”.</p> </dd></dl> <dl class="method"> <dt id="str.isdigit"> <code class="descclassname">str.</code><code class="descname">isdigit</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isdigit" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all characters in the string are digits and there is at least one character, false otherwise. Digits include decimal characters and digits that need special handling, such as the compatibility superscript digits. This covers digits which cannot be used to form numbers in base 10, like the Kharosthi numbers. Formally, a digit is a character that has the property value Numeric_Type=Digit or Numeric_Type=Decimal.</p> </dd></dl> <dl class="method"> <dt id="str.isidentifier"> <code class="descclassname">str.</code><code class="descname">isidentifier</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isidentifier" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if the string is a valid identifier according to the language definition, section <a class="reference internal" href="../reference/lexical_analysis.html#identifiers"><span class="std std-ref">Identifiers and keywords</span></a>.</p> <p>Use <a class="reference internal" href="keyword.html#keyword.iskeyword" title="keyword.iskeyword"><code class="xref py py-func docutils literal notranslate"><span class="pre">keyword.iskeyword()</span></code></a> to test for reserved identifiers such as <a class="reference internal" href="../reference/compound_stmts.html#def"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">def</span></code></a> and <a class="reference internal" href="../reference/compound_stmts.html#class"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">class</span></code></a>.</p> </dd></dl> <dl class="method"> <dt id="str.islower"> <code class="descclassname">str.</code><code class="descname">islower</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.islower" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all cased characters <a class="footnote-reference" href="#id15" id="id6">[4]</a> in the string are lowercase and there is at least one cased character, false otherwise.</p> </dd></dl> <dl class="method"> <dt id="str.isnumeric"> <code class="descclassname">str.</code><code class="descname">isnumeric</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isnumeric" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all characters in the string are numeric characters, and there is at least one character, false otherwise. Numeric characters include digit characters, and all characters that have the Unicode numeric value property, e.g. U+2155, VULGAR FRACTION ONE FIFTH. Formally, numeric characters are those with the property value Numeric_Type=Digit, Numeric_Type=Decimal or Numeric_Type=Numeric.</p> </dd></dl> <dl class="method"> <dt id="str.isprintable"> <code class="descclassname">str.</code><code class="descname">isprintable</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isprintable" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all characters in the string are printable or the string is empty, false otherwise. Nonprintable characters are those characters defined in the Unicode character database as “Other” or “Separator”, excepting the ASCII space (0x20) which is considered printable. (Note that printable characters in this context are those which should not be escaped when <a class="reference internal" href="functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate"><span class="pre">repr()</span></code></a> is invoked on a string. It has no bearing on the handling of strings written to <a class="reference internal" href="sys.html#sys.stdout" title="sys.stdout"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stdout</span></code></a> or <a class="reference internal" href="sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stderr</span></code></a>.)</p> </dd></dl> <dl class="method"> <dt id="str.isspace"> <code class="descclassname">str.</code><code class="descname">isspace</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isspace" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if there are only whitespace characters in the string and there is at least one character, false otherwise. Whitespace characters are those characters defined in the Unicode character database as “Other” or “Separator” and those with bidirectional property being one of “WS”, “B”, or “S”.</p> </dd></dl> <dl class="method"> <dt id="str.istitle"> <code class="descclassname">str.</code><code class="descname">istitle</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.istitle" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if the string is a titlecased string and there is at least one character, for example uppercase characters may only follow uncased characters and lowercase characters only cased ones. Return false otherwise.</p> </dd></dl> <dl class="method"> <dt id="str.isupper"> <code class="descclassname">str.</code><code class="descname">isupper</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.isupper" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all cased characters <a class="footnote-reference" href="#id15" id="id7">[4]</a> in the string are uppercase and there is at least one cased character, false otherwise.</p> </dd></dl> <dl class="method"> <dt id="str.join"> <code class="descclassname">str.</code><code class="descname">join</code><span class="sig-paren">(</span><em>iterable</em><span class="sig-paren">)</span><a class="headerlink" href="#str.join" title="Permalink to this definition">¶</a></dt> <dd><p>Return a string which is the concatenation of the strings in <em>iterable</em>. A <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> will be raised if there are any non-string values in <em>iterable</em>, including <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects. The separator between elements is the string providing this method.</p> </dd></dl> <dl class="method"> <dt id="str.ljust"> <code class="descclassname">str.</code><code class="descname">ljust</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillchar</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.ljust" title="Permalink to this definition">¶</a></dt> <dd><p>Return the string left justified in a string of length <em>width</em>. Padding is done using the specified <em>fillchar</em> (default is an ASCII space). The original string is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> </dd></dl> <dl class="method"> <dt id="str.lower"> <code class="descclassname">str.</code><code class="descname">lower</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.lower" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with all the cased characters <a class="footnote-reference" href="#id15" id="id8">[4]</a> converted to lowercase.</p> <p>The lowercasing algorithm used is described in section 3.13 of the Unicode Standard.</p> </dd></dl> <dl class="method"> <dt id="str.lstrip"> <code class="descclassname">str.</code><code class="descname">lstrip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.lstrip" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with leading characters removed. The <em>chars</em> argument is a string specifying the set of characters to be removed. If omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>chars</em> argument defaults to removing whitespace. The <em>chars</em> argument is not a prefix; rather, all combinations of its values are stripped:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">' spacious '</span><span class="o">.</span><span class="n">lstrip</span><span class="p">()</span> <span class="go">'spacious '</span> <span class="gp">>>> </span><span class="s1">'www.example.com'</span><span class="o">.</span><span class="n">lstrip</span><span class="p">(</span><span class="s1">'cmowz.'</span><span class="p">)</span> <span class="go">'example.com'</span> </pre></div> </div> </dd></dl> <dl class="staticmethod"> <dt id="str.maketrans"> <em class="property">static </em><code class="descclassname">str.</code><code class="descname">maketrans</code><span class="sig-paren">(</span><em>x</em><span class="optional">[</span>, <em>y</em><span class="optional">[</span>, <em>z</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.maketrans" title="Permalink to this definition">¶</a></dt> <dd><p>This static method returns a translation table usable for <a class="reference internal" href="#str.translate" title="str.translate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.translate()</span></code></a>.</p> <p>If there is only one argument, it must be a dictionary mapping Unicode ordinals (integers) or characters (strings of length 1) to Unicode ordinals, strings (of arbitrary lengths) or <code class="docutils literal notranslate"><span class="pre">None</span></code>. Character keys will then be converted to ordinals.</p> <p>If there are two arguments, they must be strings of equal length, and in the resulting dictionary, each character in x will be mapped to the character at the same position in y. If there is a third argument, it must be a string, whose characters will be mapped to <code class="docutils literal notranslate"><span class="pre">None</span></code> in the result.</p> </dd></dl> <dl class="method"> <dt id="str.partition"> <code class="descclassname">str.</code><code class="descname">partition</code><span class="sig-paren">(</span><em>sep</em><span class="sig-paren">)</span><a class="headerlink" href="#str.partition" title="Permalink to this definition">¶</a></dt> <dd><p>Split the string at the first occurrence of <em>sep</em>, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing the string itself, followed by two empty strings.</p> </dd></dl> <dl class="method"> <dt id="str.replace"> <code class="descclassname">str.</code><code class="descname">replace</code><span class="sig-paren">(</span><em>old</em>, <em>new</em><span class="optional">[</span>, <em>count</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.replace" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with all occurrences of substring <em>old</em> replaced by <em>new</em>. If the optional argument <em>count</em> is given, only the first <em>count</em> occurrences are replaced.</p> </dd></dl> <dl class="method"> <dt id="str.rfind"> <code class="descclassname">str.</code><code class="descname">rfind</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.rfind" title="Permalink to this definition">¶</a></dt> <dd><p>Return the highest index in the string where substring <em>sub</em> is found, such that <em>sub</em> is contained within <code class="docutils literal notranslate"><span class="pre">s[start:end]</span></code>. Optional arguments <em>start</em> and <em>end</em> are interpreted as in slice notation. Return <code class="docutils literal notranslate"><span class="pre">-1</span></code> on failure.</p> </dd></dl> <dl class="method"> <dt id="str.rindex"> <code class="descclassname">str.</code><code class="descname">rindex</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.rindex" title="Permalink to this definition">¶</a></dt> <dd><p>Like <a class="reference internal" href="#str.rfind" title="str.rfind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">rfind()</span></code></a> but raises <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when the substring <em>sub</em> is not found.</p> </dd></dl> <dl class="method"> <dt id="str.rjust"> <code class="descclassname">str.</code><code class="descname">rjust</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillchar</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.rjust" title="Permalink to this definition">¶</a></dt> <dd><p>Return the string right justified in a string of length <em>width</em>. Padding is done using the specified <em>fillchar</em> (default is an ASCII space). The original string is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> </dd></dl> <dl class="method"> <dt id="str.rpartition"> <code class="descclassname">str.</code><code class="descname">rpartition</code><span class="sig-paren">(</span><em>sep</em><span class="sig-paren">)</span><a class="headerlink" href="#str.rpartition" title="Permalink to this definition">¶</a></dt> <dd><p>Split the string at the last occurrence of <em>sep</em>, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing two empty strings, followed by the string itself.</p> </dd></dl> <dl class="method"> <dt id="str.rsplit"> <code class="descclassname">str.</code><code class="descname">rsplit</code><span class="sig-paren">(</span><em>sep=None</em>, <em>maxsplit=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#str.rsplit" title="Permalink to this definition">¶</a></dt> <dd><p>Return a list of the words in the string, using <em>sep</em> as the delimiter string. If <em>maxsplit</em> is given, at most <em>maxsplit</em> splits are done, the <em>rightmost</em> ones. If <em>sep</em> is not specified or <code class="docutils literal notranslate"><span class="pre">None</span></code>, any whitespace string is a separator. Except for splitting from the right, <a class="reference internal" href="#str.rsplit" title="str.rsplit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">rsplit()</span></code></a> behaves like <a class="reference internal" href="#str.split" title="str.split"><code class="xref py py-meth docutils literal notranslate"><span class="pre">split()</span></code></a> which is described in detail below.</p> </dd></dl> <dl class="method"> <dt id="str.rstrip"> <code class="descclassname">str.</code><code class="descname">rstrip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.rstrip" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with trailing characters removed. The <em>chars</em> argument is a string specifying the set of characters to be removed. If omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>chars</em> argument defaults to removing whitespace. The <em>chars</em> argument is not a suffix; rather, all combinations of its values are stripped:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">' spacious '</span><span class="o">.</span><span class="n">rstrip</span><span class="p">()</span> <span class="go">' spacious'</span> <span class="gp">>>> </span><span class="s1">'mississippi'</span><span class="o">.</span><span class="n">rstrip</span><span class="p">(</span><span class="s1">'ipz'</span><span class="p">)</span> <span class="go">'mississ'</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="str.split"> <code class="descclassname">str.</code><code class="descname">split</code><span class="sig-paren">(</span><em>sep=None</em>, <em>maxsplit=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#str.split" title="Permalink to this definition">¶</a></dt> <dd><p>Return a list of the words in the string, using <em>sep</em> as the delimiter string. If <em>maxsplit</em> is given, at most <em>maxsplit</em> splits are done (thus, the list will have at most <code class="docutils literal notranslate"><span class="pre">maxsplit+1</span></code> elements). If <em>maxsplit</em> is not specified or <code class="docutils literal notranslate"><span class="pre">-1</span></code>, then there is no limit on the number of splits (all possible splits are made).</p> <p>If <em>sep</em> is given, consecutive delimiters are not grouped together and are deemed to delimit empty strings (for example, <code class="docutils literal notranslate"><span class="pre">'1,,2'.split(',')</span></code> returns <code class="docutils literal notranslate"><span class="pre">['1',</span> <span class="pre">'',</span> <span class="pre">'2']</span></code>). The <em>sep</em> argument may consist of multiple characters (for example, <code class="docutils literal notranslate"><span class="pre">'1<>2<>3'.split('<>')</span></code> returns <code class="docutils literal notranslate"><span class="pre">['1',</span> <span class="pre">'2',</span> <span class="pre">'3']</span></code>). Splitting an empty string with a specified separator returns <code class="docutils literal notranslate"><span class="pre">['']</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'1,2,3'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">','</span><span class="p">)</span> <span class="go">['1', '2', '3']</span> <span class="gp">>>> </span><span class="s1">'1,2,3'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">','</span><span class="p">,</span> <span class="n">maxsplit</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span> <span class="go">['1', '2,3']</span> <span class="gp">>>> </span><span class="s1">'1,2,,3,'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">','</span><span class="p">)</span> <span class="go">['1', '2', '', '3', '']</span> </pre></div> </div> <p>If <em>sep</em> is not specified or is <code class="docutils literal notranslate"><span class="pre">None</span></code>, a different splitting algorithm is applied: runs of consecutive whitespace are regarded as a single separator, and the result will contain no empty strings at the start or end if the string has leading or trailing whitespace. Consequently, splitting an empty string or a string consisting of just whitespace with a <code class="docutils literal notranslate"><span class="pre">None</span></code> separator returns <code class="docutils literal notranslate"><span class="pre">[]</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'1 2 3'</span><span class="o">.</span><span class="n">split</span><span class="p">()</span> <span class="go">['1', '2', '3']</span> <span class="gp">>>> </span><span class="s1">'1 2 3'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">maxsplit</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span> <span class="go">['1', '2 3']</span> <span class="gp">>>> </span><span class="s1">' 1 2 3 '</span><span class="o">.</span><span class="n">split</span><span class="p">()</span> <span class="go">['1', '2', '3']</span> </pre></div> </div> </dd></dl> <span class="target" id="index-32"></span><dl class="method"> <dt id="str.splitlines"> <code class="descclassname">str.</code><code class="descname">splitlines</code><span class="sig-paren">(</span><span class="optional">[</span><em>keepends</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.splitlines" title="Permalink to this definition">¶</a></dt> <dd><p>Return a list of the lines in the string, breaking at line boundaries. Line breaks are not included in the resulting list unless <em>keepends</em> is given and true.</p> <p>This method splits on the following line boundaries. In particular, the boundaries are a superset of <a class="reference internal" href="../glossary.html#term-universal-newlines"><span class="xref std std-term">universal newlines</span></a>.</p> <table border="1" class="docutils"> <colgroup> <col width="44%" /> <col width="56%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Representation</th> <th class="head">Description</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">\n</span></code></td> <td>Line Feed</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">\r</span></code></td> <td>Carriage Return</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">\r\n</span></code></td> <td>Carriage Return + Line Feed</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">\v</span></code> or <code class="docutils literal notranslate"><span class="pre">\x0b</span></code></td> <td>Line Tabulation</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">\f</span></code> or <code class="docutils literal notranslate"><span class="pre">\x0c</span></code></td> <td>Form Feed</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">\x1c</span></code></td> <td>File Separator</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">\x1d</span></code></td> <td>Group Separator</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">\x1e</span></code></td> <td>Record Separator</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">\x85</span></code></td> <td>Next Line (C1 Control Code)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">\u2028</span></code></td> <td>Line Separator</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">\u2029</span></code></td> <td>Paragraph Separator</td> </tr> </tbody> </table> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.2: </span><code class="docutils literal notranslate"><span class="pre">\v</span></code> and <code class="docutils literal notranslate"><span class="pre">\f</span></code> added to list of line boundaries.</p> </div> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'ab c</span><span class="se">\n\n</span><span class="s1">de fg</span><span class="se">\r</span><span class="s1">kl</span><span class="se">\r\n</span><span class="s1">'</span><span class="o">.</span><span class="n">splitlines</span><span class="p">()</span> <span class="go">['ab c', '', 'de fg', 'kl']</span> <span class="gp">>>> </span><span class="s1">'ab c</span><span class="se">\n\n</span><span class="s1">de fg</span><span class="se">\r</span><span class="s1">kl</span><span class="se">\r\n</span><span class="s1">'</span><span class="o">.</span><span class="n">splitlines</span><span class="p">(</span><span class="n">keepends</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="go">['ab c\n', '\n', 'de fg\r', 'kl\r\n']</span> </pre></div> </div> <p>Unlike <a class="reference internal" href="#str.split" title="str.split"><code class="xref py py-meth docutils literal notranslate"><span class="pre">split()</span></code></a> when a delimiter string <em>sep</em> is given, this method returns an empty list for the empty string, and a terminal line break does not result in an extra line:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s2">""</span><span class="o">.</span><span class="n">splitlines</span><span class="p">()</span> <span class="go">[]</span> <span class="gp">>>> </span><span class="s2">"One line</span><span class="se">\n</span><span class="s2">"</span><span class="o">.</span><span class="n">splitlines</span><span class="p">()</span> <span class="go">['One line']</span> </pre></div> </div> <p>For comparison, <code class="docutils literal notranslate"><span class="pre">split('\n')</span></code> gives:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">''</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> <span class="go">['']</span> <span class="gp">>>> </span><span class="s1">'Two lines</span><span class="se">\n</span><span class="s1">'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> <span class="go">['Two lines', '']</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="str.startswith"> <code class="descclassname">str.</code><code class="descname">startswith</code><span class="sig-paren">(</span><em>prefix</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.startswith" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if string starts with the <em>prefix</em>, otherwise return <code class="docutils literal notranslate"><span class="pre">False</span></code>. <em>prefix</em> can also be a tuple of prefixes to look for. With optional <em>start</em>, test string beginning at that position. With optional <em>end</em>, stop comparing string at that position.</p> </dd></dl> <dl class="method"> <dt id="str.strip"> <code class="descclassname">str.</code><code class="descname">strip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#str.strip" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with the leading and trailing characters removed. The <em>chars</em> argument is a string specifying the set of characters to be removed. If omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>chars</em> argument defaults to removing whitespace. The <em>chars</em> argument is not a prefix or suffix; rather, all combinations of its values are stripped:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">' spacious '</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span> <span class="go">'spacious'</span> <span class="gp">>>> </span><span class="s1">'www.example.com'</span><span class="o">.</span><span class="n">strip</span><span class="p">(</span><span class="s1">'cmowz.'</span><span class="p">)</span> <span class="go">'example'</span> </pre></div> </div> <p>The outermost leading and trailing <em>chars</em> argument values are stripped from the string. Characters are removed from the leading end until reaching a string character that is not contained in the set of characters in <em>chars</em>. A similar action takes place on the trailing end. For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">comment_string</span> <span class="o">=</span> <span class="s1">'#....... Section 3.2.1 Issue #32 .......'</span> <span class="gp">>>> </span><span class="n">comment_string</span><span class="o">.</span><span class="n">strip</span><span class="p">(</span><span class="s1">'.#! '</span><span class="p">)</span> <span class="go">'Section 3.2.1 Issue #32'</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="str.swapcase"> <code class="descclassname">str.</code><code class="descname">swapcase</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.swapcase" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with uppercase characters converted to lowercase and vice versa. Note that it is not necessarily true that <code class="docutils literal notranslate"><span class="pre">s.swapcase().swapcase()</span> <span class="pre">==</span> <span class="pre">s</span></code>.</p> </dd></dl> <dl class="method"> <dt id="str.title"> <code class="descclassname">str.</code><code class="descname">title</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.title" title="Permalink to this definition">¶</a></dt> <dd><p>Return a titlecased version of the string where words start with an uppercase character and the remaining characters are lowercase.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'Hello world'</span><span class="o">.</span><span class="n">title</span><span class="p">()</span> <span class="go">'Hello World'</span> </pre></div> </div> <p>The algorithm uses a simple language-independent definition of a word as groups of consecutive letters. The definition works in many contexts but it means that apostrophes in contractions and possessives form word boundaries, which may not be the desired result:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s2">"they're bill's friends from the UK"</span><span class="o">.</span><span class="n">title</span><span class="p">()</span> <span class="go">"They'Re Bill'S Friends From The Uk"</span> </pre></div> </div> <p>A workaround for apostrophes can be constructed using regular expressions:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">re</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">titlecase</span><span class="p">(</span><span class="n">s</span><span class="p">):</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">re</span><span class="o">.</span><span class="n">sub</span><span class="p">(</span><span class="sa">r</span><span class="s2">"[A-Za-z]+('[A-Za-z]+)?"</span><span class="p">,</span> <span class="gp">... </span> <span class="k">lambda</span> <span class="n">mo</span><span class="p">:</span> <span class="n">mo</span><span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="mi">0</span><span class="p">)[</span><span class="mi">0</span><span class="p">]</span><span class="o">.</span><span class="n">upper</span><span class="p">()</span> <span class="o">+</span> <span class="gp">... </span> <span class="n">mo</span><span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="mi">0</span><span class="p">)[</span><span class="mi">1</span><span class="p">:]</span><span class="o">.</span><span class="n">lower</span><span class="p">(),</span> <span class="gp">... </span> <span class="n">s</span><span class="p">)</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">titlecase</span><span class="p">(</span><span class="s2">"they're bill's friends."</span><span class="p">)</span> <span class="go">"They're Bill's Friends."</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="str.translate"> <code class="descclassname">str.</code><code class="descname">translate</code><span class="sig-paren">(</span><em>table</em><span class="sig-paren">)</span><a class="headerlink" href="#str.translate" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string in which each character has been mapped through the given translation table. The table must be an object that implements indexing via <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__getitem__()</span></code></a>, typically a <a class="reference internal" href="../glossary.html#term-mapping"><span class="xref std std-term">mapping</span></a> or <a class="reference internal" href="../glossary.html#term-sequence"><span class="xref std std-term">sequence</span></a>. When indexed by a Unicode ordinal (an integer), the table object can do any of the following: return a Unicode ordinal or a string, to map the character to one or more other characters; return <code class="docutils literal notranslate"><span class="pre">None</span></code>, to delete the character from the return string; or raise a <a class="reference internal" href="exceptions.html#LookupError" title="LookupError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">LookupError</span></code></a> exception, to map the character to itself.</p> <p>You can use <a class="reference internal" href="#str.maketrans" title="str.maketrans"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.maketrans()</span></code></a> to create a translation map from character-to-character mappings in different formats.</p> <p>See also the <a class="reference internal" href="codecs.html#module-codecs" title="codecs: Encode and decode data and streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">codecs</span></code></a> module for a more flexible approach to custom character mappings.</p> </dd></dl> <dl class="method"> <dt id="str.upper"> <code class="descclassname">str.</code><code class="descname">upper</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#str.upper" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string with all the cased characters <a class="footnote-reference" href="#id15" id="id9">[4]</a> converted to uppercase. Note that <code class="docutils literal notranslate"><span class="pre">s.upper().isupper()</span></code> might be <code class="docutils literal notranslate"><span class="pre">False</span></code> if <code class="docutils literal notranslate"><span class="pre">s</span></code> contains uncased characters or if the Unicode category of the resulting character(s) is not “Lu” (Letter, uppercase), but e.g. “Lt” (Letter, titlecase).</p> <p>The uppercasing algorithm used is described in section 3.13 of the Unicode Standard.</p> </dd></dl> <dl class="method"> <dt id="str.zfill"> <code class="descclassname">str.</code><code class="descname">zfill</code><span class="sig-paren">(</span><em>width</em><span class="sig-paren">)</span><a class="headerlink" href="#str.zfill" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the string left filled with ASCII <code class="docutils literal notranslate"><span class="pre">'0'</span></code> digits to make a string of length <em>width</em>. A leading sign prefix (<code class="docutils literal notranslate"><span class="pre">'+'</span></code>/<code class="docutils literal notranslate"><span class="pre">'-'</span></code>) is handled by inserting the padding <em>after</em> the sign character rather than before. The original string is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s2">"42"</span><span class="o">.</span><span class="n">zfill</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="go">'00042'</span> <span class="gp">>>> </span><span class="s2">"-42"</span><span class="o">.</span><span class="n">zfill</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="go">'-0042'</span> </pre></div> </div> </dd></dl> </div> <div class="section" id="printf-style-string-formatting"> <span id="old-string-formatting"></span><h3>4.7.2. <code class="docutils literal notranslate"><span class="pre">printf</span></code>-style String Formatting<a class="headerlink" href="#printf-style-string-formatting" title="Permalink to this headline">¶</a></h3> <div class="admonition note" id="index-33"> <p class="first admonition-title">Note</p> <p class="last">The formatting operations described here exhibit a variety of quirks that lead to a number of common errors (such as failing to display tuples and dictionaries correctly). Using the newer <a class="reference internal" href="../reference/lexical_analysis.html#f-strings"><span class="std std-ref">formatted string literals</span></a> or the <a class="reference internal" href="#str.format" title="str.format"><code class="xref py py-meth docutils literal notranslate"><span class="pre">str.format()</span></code></a> interface helps avoid these errors. These alternatives also provide more powerful, flexible and extensible approaches to formatting text.</p> </div> <p>String objects have one unique built-in operation: the <code class="docutils literal notranslate"><span class="pre">%</span></code> operator (modulo). This is also known as the string <em>formatting</em> or <em>interpolation</em> operator. Given <code class="docutils literal notranslate"><span class="pre">format</span> <span class="pre">%</span> <span class="pre">values</span></code> (where <em>format</em> is a string), <code class="docutils literal notranslate"><span class="pre">%</span></code> conversion specifications in <em>format</em> are replaced with zero or more elements of <em>values</em>. The effect is similar to using the <code class="xref c c-func docutils literal notranslate"><span class="pre">sprintf()</span></code> in the C language.</p> <p>If <em>format</em> requires a single argument, <em>values</em> may be a single non-tuple object. <a class="footnote-reference" href="#id16" id="id10">[5]</a> Otherwise, <em>values</em> must be a tuple with exactly the number of items specified by the format string, or a single mapping object (for example, a dictionary).</p> <p>A conversion specifier contains two or more characters and has the following components, which must occur in this order:</p> <ol class="arabic simple"> <li>The <code class="docutils literal notranslate"><span class="pre">'%'</span></code> character, which marks the start of the specifier.</li> <li>Mapping key (optional), consisting of a parenthesised sequence of characters (for example, <code class="docutils literal notranslate"><span class="pre">(somename)</span></code>).</li> <li>Conversion flags (optional), which affect the result of some conversion types.</li> <li>Minimum field width (optional). If specified as an <code class="docutils literal notranslate"><span class="pre">'*'</span></code> (asterisk), the actual width is read from the next element of the tuple in <em>values</em>, and the object to convert comes after the minimum field width and optional precision.</li> <li>Precision (optional), given as a <code class="docutils literal notranslate"><span class="pre">'.'</span></code> (dot) followed by the precision. If specified as <code class="docutils literal notranslate"><span class="pre">'*'</span></code> (an asterisk), the actual precision is read from the next element of the tuple in <em>values</em>, and the value to convert comes after the precision.</li> <li>Length modifier (optional).</li> <li>Conversion type.</li> </ol> <p>When the right argument is a dictionary (or other mapping type), then the formats in the string <em>must</em> include a parenthesised mapping key into that dictionary inserted immediately after the <code class="docutils literal notranslate"><span class="pre">'%'</span></code> character. The mapping key selects the value to be formatted from the mapping. For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="s1">'</span><span class="si">%(language)s</span><span class="s1"> has </span><span class="si">%(number)03d</span><span class="s1"> quote types.'</span> <span class="o">%</span> <span class="gp">... </span> <span class="p">{</span><span class="s1">'language'</span><span class="p">:</span> <span class="s2">"Python"</span><span class="p">,</span> <span class="s2">"number"</span><span class="p">:</span> <span class="mi">2</span><span class="p">})</span> <span class="go">Python has 002 quote types.</span> </pre></div> </div> <p>In this case no <code class="docutils literal notranslate"><span class="pre">*</span></code> specifiers may occur in a format (since they require a sequential parameter list).</p> <p>The conversion flag characters are:</p> <table border="1" class="docutils"> <colgroup> <col width="12%" /> <col width="88%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Flag</th> <th class="head">Meaning</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'#'</span></code></td> <td>The value conversion will use the “alternate form” (where defined below).</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'0'</span></code></td> <td>The conversion will be zero padded for numeric values.</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'-'</span></code></td> <td>The converted value is left adjusted (overrides the <code class="docutils literal notranslate"><span class="pre">'0'</span></code> conversion if both are given).</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'</span> <span class="pre">'</span></code></td> <td>(a space) A blank should be left before a positive number (or empty string) produced by a signed conversion.</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'+'</span></code></td> <td>A sign character (<code class="docutils literal notranslate"><span class="pre">'+'</span></code> or <code class="docutils literal notranslate"><span class="pre">'-'</span></code>) will precede the conversion (overrides a “space” flag).</td> </tr> </tbody> </table> <p>A length modifier (<code class="docutils literal notranslate"><span class="pre">h</span></code>, <code class="docutils literal notranslate"><span class="pre">l</span></code>, or <code class="docutils literal notranslate"><span class="pre">L</span></code>) may be present, but is ignored as it is not necessary for Python – so e.g. <code class="docutils literal notranslate"><span class="pre">%ld</span></code> is identical to <code class="docutils literal notranslate"><span class="pre">%d</span></code>.</p> <p>The conversion types are:</p> <table border="1" class="docutils"> <colgroup> <col width="17%" /> <col width="74%" /> <col width="10%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Conversion</th> <th class="head">Meaning</th> <th class="head">Notes</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'d'</span></code></td> <td>Signed integer decimal.</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'i'</span></code></td> <td>Signed integer decimal.</td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'o'</span></code></td> <td>Signed octal value.</td> <td>(1)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'u'</span></code></td> <td>Obsolete type – it is identical to <code class="docutils literal notranslate"><span class="pre">'d'</span></code>.</td> <td>(6)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'x'</span></code></td> <td>Signed hexadecimal (lowercase).</td> <td>(2)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'X'</span></code></td> <td>Signed hexadecimal (uppercase).</td> <td>(2)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'e'</span></code></td> <td>Floating point exponential format (lowercase).</td> <td>(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'E'</span></code></td> <td>Floating point exponential format (uppercase).</td> <td>(3)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'f'</span></code></td> <td>Floating point decimal format.</td> <td>(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'F'</span></code></td> <td>Floating point decimal format.</td> <td>(3)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'g'</span></code></td> <td>Floating point format. Uses lowercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.</td> <td>(4)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'G'</span></code></td> <td>Floating point format. Uses uppercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.</td> <td>(4)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'c'</span></code></td> <td>Single character (accepts integer or single character string).</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'r'</span></code></td> <td>String (converts any Python object using <a class="reference internal" href="functions.html#repr" title="repr"><code class="xref py py-func docutils literal notranslate"><span class="pre">repr()</span></code></a>).</td> <td>(5)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'s'</span></code></td> <td>String (converts any Python object using <a class="reference internal" href="#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a>).</td> <td>(5)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'a'</span></code></td> <td>String (converts any Python object using <a class="reference internal" href="functions.html#ascii" title="ascii"><code class="xref py py-func docutils literal notranslate"><span class="pre">ascii()</span></code></a>).</td> <td>(5)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'%'</span></code></td> <td>No argument is converted, results in a <code class="docutils literal notranslate"><span class="pre">'%'</span></code> character in the result.</td> <td> </td> </tr> </tbody> </table> <p>Notes:</p> <ol class="arabic"> <li><p class="first">The alternate form causes a leading octal specifier (<code class="docutils literal notranslate"><span class="pre">'0o'</span></code>) to be inserted before the first digit.</p> </li> <li><p class="first">The alternate form causes a leading <code class="docutils literal notranslate"><span class="pre">'0x'</span></code> or <code class="docutils literal notranslate"><span class="pre">'0X'</span></code> (depending on whether the <code class="docutils literal notranslate"><span class="pre">'x'</span></code> or <code class="docutils literal notranslate"><span class="pre">'X'</span></code> format was used) to be inserted before the first digit.</p> </li> <li><p class="first">The alternate form causes the result to always contain a decimal point, even if no digits follow it.</p> <p>The precision determines the number of digits after the decimal point and defaults to 6.</p> </li> <li><p class="first">The alternate form causes the result to always contain a decimal point, and trailing zeroes are not removed as they would otherwise be.</p> <p>The precision determines the number of significant digits before and after the decimal point and defaults to 6.</p> </li> <li><p class="first">If precision is <code class="docutils literal notranslate"><span class="pre">N</span></code>, the output is truncated to <code class="docutils literal notranslate"><span class="pre">N</span></code> characters.</p> </li> <li><p class="first">See <span class="target" id="index-34"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0237"><strong>PEP 237</strong></a>.</p> </li> </ol> <p>Since Python strings have an explicit length, <code class="docutils literal notranslate"><span class="pre">%s</span></code> conversions do not assume that <code class="docutils literal notranslate"><span class="pre">'\0'</span></code> is the end of the string.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.1: </span><code class="docutils literal notranslate"><span class="pre">%f</span></code> conversions for numbers whose absolute value is over 1e50 are no longer replaced by <code class="docutils literal notranslate"><span class="pre">%g</span></code> conversions.</p> </div> </div> </div> <div class="section" id="binary-sequence-types-bytes-bytearray-memoryview"> <span id="binaryseq"></span><span id="index-35"></span><h2>4.8. Binary Sequence Types — <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a>, <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>, <a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a><a class="headerlink" href="#binary-sequence-types-bytes-bytearray-memoryview" title="Permalink to this headline">¶</a></h2> <p id="index-36">The core built-in types for manipulating binary data are <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> and <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>. They are supported by <a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> which uses the <a class="reference internal" href="../c-api/buffer.html#bufferobjects"><span class="std std-ref">buffer protocol</span></a> to access the memory of other binary objects without needing to make a copy.</p> <p>The <a class="reference internal" href="array.html#module-array" title="array: Space efficient arrays of uniformly typed numeric values."><code class="xref py py-mod docutils literal notranslate"><span class="pre">array</span></code></a> module supports efficient storage of basic data types like 32-bit integers and IEEE754 double-precision floating values.</p> <div class="section" id="bytes-objects"> <span id="typebytes"></span><h3>4.8.1. Bytes Objects<a class="headerlink" href="#bytes-objects" title="Permalink to this headline">¶</a></h3> <p id="index-37">Bytes objects are immutable sequences of single bytes. Since many major binary protocols are based on the ASCII text encoding, bytes objects offer several methods that are only valid when working with ASCII compatible data and are closely related to string objects in a variety of other ways.</p> <dl class="class"> <dt id="bytes"> <em class="property">class </em><code class="descname">bytes</code><span class="sig-paren">(</span><span class="optional">[</span><em>source</em><span class="optional">[</span>, <em>encoding</em><span class="optional">[</span>, <em>errors</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes" title="Permalink to this definition">¶</a></dt> <dd><p>Firstly, the syntax for bytes literals is largely the same as that for string literals, except that a <code class="docutils literal notranslate"><span class="pre">b</span></code> prefix is added:</p> <ul class="simple"> <li>Single quotes: <code class="docutils literal notranslate"><span class="pre">b'still</span> <span class="pre">allows</span> <span class="pre">embedded</span> <span class="pre">"double"</span> <span class="pre">quotes'</span></code></li> <li>Double quotes: <code class="docutils literal notranslate"><span class="pre">b"still</span> <span class="pre">allows</span> <span class="pre">embedded</span> <span class="pre">'single'</span> <span class="pre">quotes"</span></code>.</li> <li>Triple quoted: <code class="docutils literal notranslate"><span class="pre">b'''3</span> <span class="pre">single</span> <span class="pre">quotes'''</span></code>, <code class="docutils literal notranslate"><span class="pre">b"""3</span> <span class="pre">double</span> <span class="pre">quotes"""</span></code></li> </ul> <p>Only ASCII characters are permitted in bytes literals (regardless of the declared source code encoding). Any binary values over 127 must be entered into bytes literals using the appropriate escape sequence.</p> <p>As with string literals, bytes literals may also use a <code class="docutils literal notranslate"><span class="pre">r</span></code> prefix to disable processing of escape sequences. See <a class="reference internal" href="../reference/lexical_analysis.html#strings"><span class="std std-ref">String and Bytes literals</span></a> for more about the various forms of bytes literal, including supported escape sequences.</p> <p>While bytes literals and representations are based on ASCII text, bytes objects actually behave like immutable sequences of integers, with each value in the sequence restricted such that <code class="docutils literal notranslate"><span class="pre">0</span> <span class="pre"><=</span> <span class="pre">x</span> <span class="pre"><</span> <span class="pre">256</span></code> (attempts to violate this restriction will trigger <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>). This is done deliberately to emphasise that while many binary formats include ASCII based elements and can be usefully manipulated with some text-oriented algorithms, this is not generally the case for arbitrary binary data (blindly applying text processing algorithms to binary data formats that are not ASCII compatible will usually lead to data corruption).</p> <p>In addition to the literal forms, bytes objects can be created in a number of other ways:</p> <ul class="simple"> <li>A zero-filled bytes object of a specified length: <code class="docutils literal notranslate"><span class="pre">bytes(10)</span></code></li> <li>From an iterable of integers: <code class="docutils literal notranslate"><span class="pre">bytes(range(20))</span></code></li> <li>Copying existing binary data via the buffer protocol: <code class="docutils literal notranslate"><span class="pre">bytes(obj)</span></code></li> </ul> <p>Also see the <a class="reference internal" href="functions.html#func-bytes"><span class="std std-ref">bytes</span></a> built-in.</p> <p>Since 2 hexadecimal digits correspond precisely to a single byte, hexadecimal numbers are a commonly used format for describing binary data. Accordingly, the bytes type has an additional class method to read data in that format:</p> <dl class="classmethod"> <dt id="bytes.fromhex"> <em class="property">classmethod </em><code class="descname">fromhex</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.fromhex" title="Permalink to this definition">¶</a></dt> <dd><p>This <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> class method returns a bytes object, decoding the given string object. The string must contain two hexadecimal digits per byte, with ASCII whitespace being ignored.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">bytes</span><span class="o">.</span><span class="n">fromhex</span><span class="p">(</span><span class="s1">'2Ef0 F1f2 '</span><span class="p">)</span> <span class="go">b'.\xf0\xf1\xf2'</span> </pre></div> </div> </dd></dl> <p>A reverse conversion function exists to transform a bytes object into its hexadecimal representation.</p> <dl class="method"> <dt id="bytes.hex"> <code class="descname">hex</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.hex" title="Permalink to this definition">¶</a></dt> <dd><p>Return a string object containing two hexadecimal digits for each byte in the instance.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'</span><span class="se">\xf0\xf1\xf2</span><span class="s1">'</span><span class="o">.</span><span class="n">hex</span><span class="p">()</span> <span class="go">'f0f1f2'</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </dd></dl> </dd></dl> <p>Since bytes objects are sequences of integers (akin to a tuple), for a bytes object <em>b</em>, <code class="docutils literal notranslate"><span class="pre">b[0]</span></code> will be an integer, while <code class="docutils literal notranslate"><span class="pre">b[0:1]</span></code> will be a bytes object of length 1. (This contrasts with text strings, where both indexing and slicing will produce a string of length 1)</p> <p>The representation of bytes objects uses the literal format (<code class="docutils literal notranslate"><span class="pre">b'...'</span></code>) since it is often more useful than e.g. <code class="docutils literal notranslate"><span class="pre">bytes([46,</span> <span class="pre">46,</span> <span class="pre">46])</span></code>. You can always convert a bytes object into a list of integers using <code class="docutils literal notranslate"><span class="pre">list(b)</span></code>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">For Python 2.x users: In the Python 2.x series, a variety of implicit conversions between 8-bit strings (the closest thing 2.x offers to a built-in binary data type) and Unicode strings were permitted. This was a backwards compatibility workaround to account for the fact that Python originally only supported 8-bit text, and Unicode text was a later addition. In Python 3.x, those implicit conversions are gone - conversions between 8-bit binary data and Unicode text must be explicit, and bytes and string objects will always compare unequal.</p> </div> </div> <div class="section" id="bytearray-objects"> <span id="typebytearray"></span><h3>4.8.2. Bytearray Objects<a class="headerlink" href="#bytearray-objects" title="Permalink to this headline">¶</a></h3> <p id="index-38"><a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> objects are a mutable counterpart to <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects.</p> <dl class="class"> <dt id="bytearray"> <em class="property">class </em><code class="descname">bytearray</code><span class="sig-paren">(</span><span class="optional">[</span><em>source</em><span class="optional">[</span>, <em>encoding</em><span class="optional">[</span>, <em>errors</em><span class="optional">]</span><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray" title="Permalink to this definition">¶</a></dt> <dd><p>There is no dedicated literal syntax for bytearray objects, instead they are always created by calling the constructor:</p> <ul class="simple"> <li>Creating an empty instance: <code class="docutils literal notranslate"><span class="pre">bytearray()</span></code></li> <li>Creating a zero-filled instance with a given length: <code class="docutils literal notranslate"><span class="pre">bytearray(10)</span></code></li> <li>From an iterable of integers: <code class="docutils literal notranslate"><span class="pre">bytearray(range(20))</span></code></li> <li>Copying existing binary data via the buffer protocol: <code class="docutils literal notranslate"><span class="pre">bytearray(b'Hi!')</span></code></li> </ul> <p>As bytearray objects are mutable, they support the <a class="reference internal" href="#typesseq-mutable"><span class="std std-ref">mutable</span></a> sequence operations in addition to the common bytes and bytearray operations described in <a class="reference internal" href="#bytes-methods"><span class="std std-ref">Bytes and Bytearray Operations</span></a>.</p> <p>Also see the <a class="reference internal" href="functions.html#func-bytearray"><span class="std std-ref">bytearray</span></a> built-in.</p> <p>Since 2 hexadecimal digits correspond precisely to a single byte, hexadecimal numbers are a commonly used format for describing binary data. Accordingly, the bytearray type has an additional class method to read data in that format:</p> <dl class="classmethod"> <dt id="bytearray.fromhex"> <em class="property">classmethod </em><code class="descname">fromhex</code><span class="sig-paren">(</span><em>string</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.fromhex" title="Permalink to this definition">¶</a></dt> <dd><p>This <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> class method returns bytearray object, decoding the given string object. The string must contain two hexadecimal digits per byte, with ASCII whitespace being ignored.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">bytearray</span><span class="o">.</span><span class="n">fromhex</span><span class="p">(</span><span class="s1">'2Ef0 F1f2 '</span><span class="p">)</span> <span class="go">bytearray(b'.\xf0\xf1\xf2')</span> </pre></div> </div> </dd></dl> <p>A reverse conversion function exists to transform a bytearray object into its hexadecimal representation.</p> <dl class="method"> <dt id="bytearray.hex"> <code class="descname">hex</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.hex" title="Permalink to this definition">¶</a></dt> <dd><p>Return a string object containing two hexadecimal digits for each byte in the instance.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">bytearray</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\xf0\xf1\xf2</span><span class="s1">'</span><span class="p">)</span><span class="o">.</span><span class="n">hex</span><span class="p">()</span> <span class="go">'f0f1f2'</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </dd></dl> </dd></dl> <p>Since bytearray objects are sequences of integers (akin to a list), for a bytearray object <em>b</em>, <code class="docutils literal notranslate"><span class="pre">b[0]</span></code> will be an integer, while <code class="docutils literal notranslate"><span class="pre">b[0:1]</span></code> will be a bytearray object of length 1. (This contrasts with text strings, where both indexing and slicing will produce a string of length 1)</p> <p>The representation of bytearray objects uses the bytes literal format (<code class="docutils literal notranslate"><span class="pre">bytearray(b'...')</span></code>) since it is often more useful than e.g. <code class="docutils literal notranslate"><span class="pre">bytearray([46,</span> <span class="pre">46,</span> <span class="pre">46])</span></code>. You can always convert a bytearray object into a list of integers using <code class="docutils literal notranslate"><span class="pre">list(b)</span></code>.</p> </div> <div class="section" id="bytes-and-bytearray-operations"> <span id="bytes-methods"></span><h3>4.8.3. Bytes and Bytearray Operations<a class="headerlink" href="#bytes-and-bytearray-operations" title="Permalink to this headline">¶</a></h3> <p id="index-39">Both bytes and bytearray objects support the <a class="reference internal" href="#typesseq-common"><span class="std std-ref">common</span></a> sequence operations. They interoperate not just with operands of the same type, but with any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>. Due to this flexibility, they can be freely mixed in operations without causing errors. However, the return type of the result may depend on the order of operands.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p>The methods on bytes and bytearray objects don’t accept strings as their arguments, just as the methods on strings don’t accept bytes as their arguments. For example, you have to write:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="o">=</span> <span class="s2">"abc"</span> <span class="n">b</span> <span class="o">=</span> <span class="n">a</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s2">"a"</span><span class="p">,</span> <span class="s2">"f"</span><span class="p">)</span> </pre></div> </div> <p>and:</p> <div class="last highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">a</span> <span class="o">=</span> <span class="sa">b</span><span class="s2">"abc"</span> <span class="n">b</span> <span class="o">=</span> <span class="n">a</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="sa">b</span><span class="s2">"a"</span><span class="p">,</span> <span class="sa">b</span><span class="s2">"f"</span><span class="p">)</span> </pre></div> </div> </div> <p>Some bytes and bytearray operations assume the use of ASCII compatible binary formats, and hence should be avoided when working with arbitrary binary data. These restrictions are covered below.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Using these ASCII based operations to manipulate binary data that is not stored in an ASCII based format may lead to data corruption.</p> </div> <p>The following methods on bytes and bytearray objects can be used with arbitrary binary data.</p> <dl class="method"> <dt id="bytes.count"> <code class="descclassname">bytes.</code><code class="descname">count</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.count" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.count"> <code class="descclassname">bytearray.</code><code class="descname">count</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.count" title="Permalink to this definition">¶</a></dt> <dd><p>Return the number of non-overlapping occurrences of subsequence <em>sub</em> in the range [<em>start</em>, <em>end</em>]. Optional arguments <em>start</em> and <em>end</em> are interpreted as in slice notation.</p> <p>The subsequence to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> or an integer in the range 0 to 255.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Also accept an integer in the range 0 to 255 as the subsequence.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.decode"> <code class="descclassname">bytes.</code><code class="descname">decode</code><span class="sig-paren">(</span><em>encoding="utf-8"</em>, <em>errors="strict"</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.decode" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.decode"> <code class="descclassname">bytearray.</code><code class="descname">decode</code><span class="sig-paren">(</span><em>encoding="utf-8"</em>, <em>errors="strict"</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.decode" title="Permalink to this definition">¶</a></dt> <dd><p>Return a string decoded from the given bytes. Default encoding is <code class="docutils literal notranslate"><span class="pre">'utf-8'</span></code>. <em>errors</em> may be given to set a different error handling scheme. The default for <em>errors</em> is <code class="docutils literal notranslate"><span class="pre">'strict'</span></code>, meaning that encoding errors raise a <a class="reference internal" href="exceptions.html#UnicodeError" title="UnicodeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">UnicodeError</span></code></a>. Other possible values are <code class="docutils literal notranslate"><span class="pre">'ignore'</span></code>, <code class="docutils literal notranslate"><span class="pre">'replace'</span></code> and any other name registered via <a class="reference internal" href="codecs.html#codecs.register_error" title="codecs.register_error"><code class="xref py py-func docutils literal notranslate"><span class="pre">codecs.register_error()</span></code></a>, see section <a class="reference internal" href="codecs.html#error-handlers"><span class="std std-ref">Error Handlers</span></a>. For a list of possible encodings, see section <a class="reference internal" href="codecs.html#standard-encodings"><span class="std std-ref">Standard Encodings</span></a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">Passing the <em>encoding</em> argument to <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> allows decoding any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> directly, without needing to make a temporary bytes or bytearray object.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.1: </span>Added support for keyword arguments.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.endswith"> <code class="descclassname">bytes.</code><code class="descname">endswith</code><span class="sig-paren">(</span><em>suffix</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.endswith" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.endswith"> <code class="descclassname">bytearray.</code><code class="descname">endswith</code><span class="sig-paren">(</span><em>suffix</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.endswith" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the binary data ends with the specified <em>suffix</em>, otherwise return <code class="docutils literal notranslate"><span class="pre">False</span></code>. <em>suffix</em> can also be a tuple of suffixes to look for. With optional <em>start</em>, test beginning at that position. With optional <em>end</em>, stop comparing at that position.</p> <p>The suffix(es) to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> </dd></dl> <dl class="method"> <dt id="bytes.find"> <code class="descclassname">bytes.</code><code class="descname">find</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.find" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.find"> <code class="descclassname">bytearray.</code><code class="descname">find</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.find" title="Permalink to this definition">¶</a></dt> <dd><p>Return the lowest index in the data where the subsequence <em>sub</em> is found, such that <em>sub</em> is contained in the slice <code class="docutils literal notranslate"><span class="pre">s[start:end]</span></code>. Optional arguments <em>start</em> and <em>end</em> are interpreted as in slice notation. Return <code class="docutils literal notranslate"><span class="pre">-1</span></code> if <em>sub</em> is not found.</p> <p>The subsequence to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> or an integer in the range 0 to 255.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p>The <a class="reference internal" href="#bytes.find" title="bytes.find"><code class="xref py py-meth docutils literal notranslate"><span class="pre">find()</span></code></a> method should be used only if you need to know the position of <em>sub</em>. To check if <em>sub</em> is a substring or not, use the <a class="reference internal" href="../reference/expressions.html#in"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">in</span></code></a> operator:</p> <div class="last highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Py'</span> <span class="ow">in</span> <span class="sa">b</span><span class="s1">'Python'</span> <span class="go">True</span> </pre></div> </div> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Also accept an integer in the range 0 to 255 as the subsequence.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.index"> <code class="descclassname">bytes.</code><code class="descname">index</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.index" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.index"> <code class="descclassname">bytearray.</code><code class="descname">index</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.index" title="Permalink to this definition">¶</a></dt> <dd><p>Like <a class="reference internal" href="#bytes.find" title="bytes.find"><code class="xref py py-meth docutils literal notranslate"><span class="pre">find()</span></code></a>, but raise <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when the subsequence is not found.</p> <p>The subsequence to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> or an integer in the range 0 to 255.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Also accept an integer in the range 0 to 255 as the subsequence.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.join"> <code class="descclassname">bytes.</code><code class="descname">join</code><span class="sig-paren">(</span><em>iterable</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.join" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.join"> <code class="descclassname">bytearray.</code><code class="descname">join</code><span class="sig-paren">(</span><em>iterable</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.join" title="Permalink to this definition">¶</a></dt> <dd><p>Return a bytes or bytearray object which is the concatenation of the binary data sequences in <em>iterable</em>. A <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> will be raised if there are any values in <em>iterable</em> that are not <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like objects</span></a>, including <a class="reference internal" href="#str" title="str"><code class="xref py py-class docutils literal notranslate"><span class="pre">str</span></code></a> objects. The separator between elements is the contents of the bytes or bytearray object providing this method.</p> </dd></dl> <dl class="staticmethod"> <dt id="bytes.maketrans"> <em class="property">static </em><code class="descclassname">bytes.</code><code class="descname">maketrans</code><span class="sig-paren">(</span><em>from</em>, <em>to</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.maketrans" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.maketrans"> <em class="property">static </em><code class="descclassname">bytearray.</code><code class="descname">maketrans</code><span class="sig-paren">(</span><em>from</em>, <em>to</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.maketrans" title="Permalink to this definition">¶</a></dt> <dd><p>This static method returns a translation table usable for <a class="reference internal" href="#bytes.translate" title="bytes.translate"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytes.translate()</span></code></a> that will map each character in <em>from</em> into the character at the same position in <em>to</em>; <em>from</em> and <em>to</em> must both be <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like objects</span></a> and have the same length.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.1.</span></p> </div> </dd></dl> <dl class="method"> <dt id="bytes.partition"> <code class="descclassname">bytes.</code><code class="descname">partition</code><span class="sig-paren">(</span><em>sep</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.partition" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.partition"> <code class="descclassname">bytearray.</code><code class="descname">partition</code><span class="sig-paren">(</span><em>sep</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.partition" title="Permalink to this definition">¶</a></dt> <dd><p>Split the sequence at the first occurrence of <em>sep</em>, and return a 3-tuple containing the part before the separator, the separator itself or its bytearray copy, and the part after the separator. If the separator is not found, return a 3-tuple containing a copy of the original sequence, followed by two empty bytes or bytearray objects.</p> <p>The separator to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> </dd></dl> <dl class="method"> <dt id="bytes.replace"> <code class="descclassname">bytes.</code><code class="descname">replace</code><span class="sig-paren">(</span><em>old</em>, <em>new</em><span class="optional">[</span>, <em>count</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.replace" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.replace"> <code class="descclassname">bytearray.</code><code class="descname">replace</code><span class="sig-paren">(</span><em>old</em>, <em>new</em><span class="optional">[</span>, <em>count</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.replace" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with all occurrences of subsequence <em>old</em> replaced by <em>new</em>. If the optional argument <em>count</em> is given, only the first <em>count</em> occurrences are replaced.</p> <p>The subsequence to search for and its replacement may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.rfind"> <code class="descclassname">bytes.</code><code class="descname">rfind</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.rfind" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.rfind"> <code class="descclassname">bytearray.</code><code class="descname">rfind</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.rfind" title="Permalink to this definition">¶</a></dt> <dd><p>Return the highest index in the sequence where the subsequence <em>sub</em> is found, such that <em>sub</em> is contained within <code class="docutils literal notranslate"><span class="pre">s[start:end]</span></code>. Optional arguments <em>start</em> and <em>end</em> are interpreted as in slice notation. Return <code class="docutils literal notranslate"><span class="pre">-1</span></code> on failure.</p> <p>The subsequence to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> or an integer in the range 0 to 255.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Also accept an integer in the range 0 to 255 as the subsequence.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.rindex"> <code class="descclassname">bytes.</code><code class="descname">rindex</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.rindex" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.rindex"> <code class="descclassname">bytearray.</code><code class="descname">rindex</code><span class="sig-paren">(</span><em>sub</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.rindex" title="Permalink to this definition">¶</a></dt> <dd><p>Like <a class="reference internal" href="#bytes.rfind" title="bytes.rfind"><code class="xref py py-meth docutils literal notranslate"><span class="pre">rfind()</span></code></a> but raises <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a> when the subsequence <em>sub</em> is not found.</p> <p>The subsequence to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a> or an integer in the range 0 to 255.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Also accept an integer in the range 0 to 255 as the subsequence.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.rpartition"> <code class="descclassname">bytes.</code><code class="descname">rpartition</code><span class="sig-paren">(</span><em>sep</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.rpartition" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.rpartition"> <code class="descclassname">bytearray.</code><code class="descname">rpartition</code><span class="sig-paren">(</span><em>sep</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.rpartition" title="Permalink to this definition">¶</a></dt> <dd><p>Split the sequence at the last occurrence of <em>sep</em>, and return a 3-tuple containing the part before the separator, the separator itself or its bytearray copy, and the part after the separator. If the separator is not found, return a 3-tuple containing a copy of the original sequence, followed by two empty bytes or bytearray objects.</p> <p>The separator to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> </dd></dl> <dl class="method"> <dt id="bytes.startswith"> <code class="descclassname">bytes.</code><code class="descname">startswith</code><span class="sig-paren">(</span><em>prefix</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.startswith" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.startswith"> <code class="descclassname">bytearray.</code><code class="descname">startswith</code><span class="sig-paren">(</span><em>prefix</em><span class="optional">[</span>, <em>start</em><span class="optional">[</span>, <em>end</em><span class="optional">]</span><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.startswith" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the binary data starts with the specified <em>prefix</em>, otherwise return <code class="docutils literal notranslate"><span class="pre">False</span></code>. <em>prefix</em> can also be a tuple of prefixes to look for. With optional <em>start</em>, test beginning at that position. With optional <em>end</em>, stop comparing at that position.</p> <p>The prefix(es) to search for may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> </dd></dl> <dl class="method"> <dt id="bytes.translate"> <code class="descclassname">bytes.</code><code class="descname">translate</code><span class="sig-paren">(</span><em>table</em>, <em>delete=b''</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.translate" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.translate"> <code class="descclassname">bytearray.</code><code class="descname">translate</code><span class="sig-paren">(</span><em>table</em>, <em>delete=b''</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.translate" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the bytes or bytearray object where all bytes occurring in the optional argument <em>delete</em> are removed, and the remaining bytes have been mapped through the given translation table, which must be a bytes object of length 256.</p> <p>You can use the <a class="reference internal" href="#bytes.maketrans" title="bytes.maketrans"><code class="xref py py-func docutils literal notranslate"><span class="pre">bytes.maketrans()</span></code></a> method to create a translation table.</p> <p>Set the <em>table</em> argument to <code class="docutils literal notranslate"><span class="pre">None</span></code> for translations that only delete characters:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'read this short text'</span><span class="o">.</span><span class="n">translate</span><span class="p">(</span><span class="kc">None</span><span class="p">,</span> <span class="sa">b</span><span class="s1">'aeiou'</span><span class="p">)</span> <span class="go">b'rd ths shrt txt'</span> </pre></div> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.6: </span><em>delete</em> is now supported as a keyword argument.</p> </div> </dd></dl> <p>The following methods on bytes and bytearray objects have default behaviours that assume the use of ASCII compatible binary formats, but can still be used with arbitrary binary data by passing appropriate arguments. Note that all of the bytearray methods in this section do <em>not</em> operate in place, and instead produce new objects.</p> <dl class="method"> <dt id="bytes.center"> <code class="descclassname">bytes.</code><code class="descname">center</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillbyte</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.center" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.center"> <code class="descclassname">bytearray.</code><code class="descname">center</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillbyte</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.center" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the object centered in a sequence of length <em>width</em>. Padding is done using the specified <em>fillbyte</em> (default is an ASCII space). For <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects, the original sequence is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.ljust"> <code class="descclassname">bytes.</code><code class="descname">ljust</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillbyte</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.ljust" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.ljust"> <code class="descclassname">bytearray.</code><code class="descname">ljust</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillbyte</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.ljust" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the object left justified in a sequence of length <em>width</em>. Padding is done using the specified <em>fillbyte</em> (default is an ASCII space). For <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects, the original sequence is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.lstrip"> <code class="descclassname">bytes.</code><code class="descname">lstrip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.lstrip" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.lstrip"> <code class="descclassname">bytearray.</code><code class="descname">lstrip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.lstrip" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with specified leading bytes removed. The <em>chars</em> argument is a binary sequence specifying the set of byte values to be removed - the name refers to the fact this method is usually used with ASCII characters. If omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>chars</em> argument defaults to removing ASCII whitespace. The <em>chars</em> argument is not a prefix; rather, all combinations of its values are stripped:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">' spacious '</span><span class="o">.</span><span class="n">lstrip</span><span class="p">()</span> <span class="go">b'spacious '</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'www.example.com'</span><span class="o">.</span><span class="n">lstrip</span><span class="p">(</span><span class="sa">b</span><span class="s1">'cmowz.'</span><span class="p">)</span> <span class="go">b'example.com'</span> </pre></div> </div> <p>The binary sequence of byte values to remove may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.rjust"> <code class="descclassname">bytes.</code><code class="descname">rjust</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillbyte</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.rjust" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.rjust"> <code class="descclassname">bytearray.</code><code class="descname">rjust</code><span class="sig-paren">(</span><em>width</em><span class="optional">[</span>, <em>fillbyte</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.rjust" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the object right justified in a sequence of length <em>width</em>. Padding is done using the specified <em>fillbyte</em> (default is an ASCII space). For <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects, the original sequence is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(s)</span></code>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.rsplit"> <code class="descclassname">bytes.</code><code class="descname">rsplit</code><span class="sig-paren">(</span><em>sep=None</em>, <em>maxsplit=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.rsplit" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.rsplit"> <code class="descclassname">bytearray.</code><code class="descname">rsplit</code><span class="sig-paren">(</span><em>sep=None</em>, <em>maxsplit=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.rsplit" title="Permalink to this definition">¶</a></dt> <dd><p>Split the binary sequence into subsequences of the same type, using <em>sep</em> as the delimiter string. If <em>maxsplit</em> is given, at most <em>maxsplit</em> splits are done, the <em>rightmost</em> ones. If <em>sep</em> is not specified or <code class="docutils literal notranslate"><span class="pre">None</span></code>, any subsequence consisting solely of ASCII whitespace is a separator. Except for splitting from the right, <a class="reference internal" href="#bytearray.rsplit" title="bytearray.rsplit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">rsplit()</span></code></a> behaves like <a class="reference internal" href="#bytearray.split" title="bytearray.split"><code class="xref py py-meth docutils literal notranslate"><span class="pre">split()</span></code></a> which is described in detail below.</p> </dd></dl> <dl class="method"> <dt id="bytes.rstrip"> <code class="descclassname">bytes.</code><code class="descname">rstrip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.rstrip" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.rstrip"> <code class="descclassname">bytearray.</code><code class="descname">rstrip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.rstrip" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with specified trailing bytes removed. The <em>chars</em> argument is a binary sequence specifying the set of byte values to be removed - the name refers to the fact this method is usually used with ASCII characters. If omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>chars</em> argument defaults to removing ASCII whitespace. The <em>chars</em> argument is not a suffix; rather, all combinations of its values are stripped:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">' spacious '</span><span class="o">.</span><span class="n">rstrip</span><span class="p">()</span> <span class="go">b' spacious'</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'mississippi'</span><span class="o">.</span><span class="n">rstrip</span><span class="p">(</span><span class="sa">b</span><span class="s1">'ipz'</span><span class="p">)</span> <span class="go">b'mississ'</span> </pre></div> </div> <p>The binary sequence of byte values to remove may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.split"> <code class="descclassname">bytes.</code><code class="descname">split</code><span class="sig-paren">(</span><em>sep=None</em>, <em>maxsplit=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.split" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.split"> <code class="descclassname">bytearray.</code><code class="descname">split</code><span class="sig-paren">(</span><em>sep=None</em>, <em>maxsplit=-1</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.split" title="Permalink to this definition">¶</a></dt> <dd><p>Split the binary sequence into subsequences of the same type, using <em>sep</em> as the delimiter string. If <em>maxsplit</em> is given and non-negative, at most <em>maxsplit</em> splits are done (thus, the list will have at most <code class="docutils literal notranslate"><span class="pre">maxsplit+1</span></code> elements). If <em>maxsplit</em> is not specified or is <code class="docutils literal notranslate"><span class="pre">-1</span></code>, then there is no limit on the number of splits (all possible splits are made).</p> <p>If <em>sep</em> is given, consecutive delimiters are not grouped together and are deemed to delimit empty subsequences (for example, <code class="docutils literal notranslate"><span class="pre">b'1,,2'.split(b',')</span></code> returns <code class="docutils literal notranslate"><span class="pre">[b'1',</span> <span class="pre">b'',</span> <span class="pre">b'2']</span></code>). The <em>sep</em> argument may consist of a multibyte sequence (for example, <code class="docutils literal notranslate"><span class="pre">b'1<>2<>3'.split(b'<>')</span></code> returns <code class="docutils literal notranslate"><span class="pre">[b'1',</span> <span class="pre">b'2',</span> <span class="pre">b'3']</span></code>). Splitting an empty sequence with a specified separator returns <code class="docutils literal notranslate"><span class="pre">[b'']</span></code> or <code class="docutils literal notranslate"><span class="pre">[bytearray(b'')]</span></code> depending on the type of object being split. The <em>sep</em> argument may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1,2,3'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="sa">b</span><span class="s1">','</span><span class="p">)</span> <span class="go">[b'1', b'2', b'3']</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1,2,3'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="sa">b</span><span class="s1">','</span><span class="p">,</span> <span class="n">maxsplit</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span> <span class="go">[b'1', b'2,3']</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1,2,,3,'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="sa">b</span><span class="s1">','</span><span class="p">)</span> <span class="go">[b'1', b'2', b'', b'3', b'']</span> </pre></div> </div> <p>If <em>sep</em> is not specified or is <code class="docutils literal notranslate"><span class="pre">None</span></code>, a different splitting algorithm is applied: runs of consecutive ASCII whitespace are regarded as a single separator, and the result will contain no empty strings at the start or end if the sequence has leading or trailing whitespace. Consequently, splitting an empty sequence or a sequence consisting solely of ASCII whitespace without a specified separator returns <code class="docutils literal notranslate"><span class="pre">[]</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1 2 3'</span><span class="o">.</span><span class="n">split</span><span class="p">()</span> <span class="go">[b'1', b'2', b'3']</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1 2 3'</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">maxsplit</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span> <span class="go">[b'1', b'2 3']</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">' 1 2 3 '</span><span class="o">.</span><span class="n">split</span><span class="p">()</span> <span class="go">[b'1', b'2', b'3']</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="bytes.strip"> <code class="descclassname">bytes.</code><code class="descname">strip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.strip" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.strip"> <code class="descclassname">bytearray.</code><code class="descname">strip</code><span class="sig-paren">(</span><span class="optional">[</span><em>chars</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.strip" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with specified leading and trailing bytes removed. The <em>chars</em> argument is a binary sequence specifying the set of byte values to be removed - the name refers to the fact this method is usually used with ASCII characters. If omitted or <code class="docutils literal notranslate"><span class="pre">None</span></code>, the <em>chars</em> argument defaults to removing ASCII whitespace. The <em>chars</em> argument is not a prefix or suffix; rather, all combinations of its values are stripped:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">' spacious '</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span> <span class="go">b'spacious'</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'www.example.com'</span><span class="o">.</span><span class="n">strip</span><span class="p">(</span><span class="sa">b</span><span class="s1">'cmowz.'</span><span class="p">)</span> <span class="go">b'example'</span> </pre></div> </div> <p>The binary sequence of byte values to remove may be any <a class="reference internal" href="../glossary.html#term-bytes-like-object"><span class="xref std std-term">bytes-like object</span></a>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <p>The following methods on bytes and bytearray objects assume the use of ASCII compatible binary formats and should not be applied to arbitrary binary data. Note that all of the bytearray methods in this section do <em>not</em> operate in place, and instead produce new objects.</p> <dl class="method"> <dt id="bytes.capitalize"> <code class="descclassname">bytes.</code><code class="descname">capitalize</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.capitalize" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.capitalize"> <code class="descclassname">bytearray.</code><code class="descname">capitalize</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.capitalize" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with each byte interpreted as an ASCII character, and the first byte capitalized and the rest lowercased. Non-ASCII byte values are passed through unchanged.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.expandtabs"> <code class="descclassname">bytes.</code><code class="descname">expandtabs</code><span class="sig-paren">(</span><em>tabsize=8</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.expandtabs" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.expandtabs"> <code class="descclassname">bytearray.</code><code class="descname">expandtabs</code><span class="sig-paren">(</span><em>tabsize=8</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.expandtabs" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence where all ASCII tab characters are replaced by one or more ASCII spaces, depending on the current column and the given tab size. Tab positions occur every <em>tabsize</em> bytes (default is 8, giving tab positions at columns 0, 8, 16 and so on). To expand the sequence, the current column is set to zero and the sequence is examined byte by byte. If the byte is an ASCII tab character (<code class="docutils literal notranslate"><span class="pre">b'\t'</span></code>), one or more space characters are inserted in the result until the current column is equal to the next tab position. (The tab character itself is not copied.) If the current byte is an ASCII newline (<code class="docutils literal notranslate"><span class="pre">b'\n'</span></code>) or carriage return (<code class="docutils literal notranslate"><span class="pre">b'\r'</span></code>), it is copied and the current column is reset to zero. Any other byte value is copied unchanged and the current column is incremented by one regardless of how the byte value is represented when printed:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'01</span><span class="se">\t</span><span class="s1">012</span><span class="se">\t</span><span class="s1">0123</span><span class="se">\t</span><span class="s1">01234'</span><span class="o">.</span><span class="n">expandtabs</span><span class="p">()</span> <span class="go">b'01 012 0123 01234'</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'01</span><span class="se">\t</span><span class="s1">012</span><span class="se">\t</span><span class="s1">0123</span><span class="se">\t</span><span class="s1">01234'</span><span class="o">.</span><span class="n">expandtabs</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span> <span class="go">b'01 012 0123 01234'</span> </pre></div> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.isalnum"> <code class="descclassname">bytes.</code><code class="descname">isalnum</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.isalnum" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.isalnum"> <code class="descclassname">bytearray.</code><code class="descname">isalnum</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.isalnum" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all bytes in the sequence are alphabetical ASCII characters or ASCII decimal digits and the sequence is not empty, false otherwise. Alphabetic ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>. ASCII decimal digits are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'0123456789'</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'ABCabc1'</span><span class="o">.</span><span class="n">isalnum</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'ABC abc1'</span><span class="o">.</span><span class="n">isalnum</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="bytes.isalpha"> <code class="descclassname">bytes.</code><code class="descname">isalpha</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.isalpha" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.isalpha"> <code class="descclassname">bytearray.</code><code class="descname">isalpha</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.isalpha" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all bytes in the sequence are alphabetic ASCII characters and the sequence is not empty, false otherwise. Alphabetic ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'ABCabc'</span><span class="o">.</span><span class="n">isalpha</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'ABCabc1'</span><span class="o">.</span><span class="n">isalpha</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="bytes.isdigit"> <code class="descclassname">bytes.</code><code class="descname">isdigit</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.isdigit" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.isdigit"> <code class="descclassname">bytearray.</code><code class="descname">isdigit</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.isdigit" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all bytes in the sequence are ASCII decimal digits and the sequence is not empty, false otherwise. ASCII decimal digits are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'0123456789'</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1234'</span><span class="o">.</span><span class="n">isdigit</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'1.23'</span><span class="o">.</span><span class="n">isdigit</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="bytes.islower"> <code class="descclassname">bytes.</code><code class="descname">islower</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.islower" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.islower"> <code class="descclassname">bytearray.</code><code class="descname">islower</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.islower" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if there is at least one lowercase ASCII character in the sequence and no uppercase ASCII characters, false otherwise.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'hello world'</span><span class="o">.</span><span class="n">islower</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello world'</span><span class="o">.</span><span class="n">islower</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> <p>Lowercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyz'</span></code>. Uppercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>.</p> </dd></dl> <dl class="method"> <dt id="bytes.isspace"> <code class="descclassname">bytes.</code><code class="descname">isspace</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.isspace" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.isspace"> <code class="descclassname">bytearray.</code><code class="descname">isspace</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.isspace" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if all bytes in the sequence are ASCII whitespace and the sequence is not empty, false otherwise. ASCII whitespace characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'</span> <span class="pre">\t\n\r\x0b\f'</span></code> (space, tab, newline, carriage return, vertical tab, form feed).</p> </dd></dl> <dl class="method"> <dt id="bytes.istitle"> <code class="descclassname">bytes.</code><code class="descname">istitle</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.istitle" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.istitle"> <code class="descclassname">bytearray.</code><code class="descname">istitle</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.istitle" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if the sequence is ASCII titlecase and the sequence is not empty, false otherwise. See <a class="reference internal" href="#bytes.title" title="bytes.title"><code class="xref py py-meth docutils literal notranslate"><span class="pre">bytes.title()</span></code></a> for more details on the definition of “titlecase”.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello World'</span><span class="o">.</span><span class="n">istitle</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello world'</span><span class="o">.</span><span class="n">istitle</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="bytes.isupper"> <code class="descclassname">bytes.</code><code class="descname">isupper</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.isupper" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.isupper"> <code class="descclassname">bytearray.</code><code class="descname">isupper</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.isupper" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if there is at least one uppercase alphabetic ASCII character in the sequence and no lowercase ASCII characters, false otherwise.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'HELLO WORLD'</span><span class="o">.</span><span class="n">isupper</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello world'</span><span class="o">.</span><span class="n">isupper</span><span class="p">()</span> <span class="go">False</span> </pre></div> </div> <p>Lowercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyz'</span></code>. Uppercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>.</p> </dd></dl> <dl class="method"> <dt id="bytes.lower"> <code class="descclassname">bytes.</code><code class="descname">lower</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.lower" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.lower"> <code class="descclassname">bytearray.</code><code class="descname">lower</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.lower" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with all the uppercase ASCII characters converted to their corresponding lowercase counterpart.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello World'</span><span class="o">.</span><span class="n">lower</span><span class="p">()</span> <span class="go">b'hello world'</span> </pre></div> </div> <p>Lowercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyz'</span></code>. Uppercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <span class="target" id="index-40"></span><dl class="method"> <dt id="bytes.splitlines"> <code class="descclassname">bytes.</code><code class="descname">splitlines</code><span class="sig-paren">(</span><em>keepends=False</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.splitlines" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.splitlines"> <code class="descclassname">bytearray.</code><code class="descname">splitlines</code><span class="sig-paren">(</span><em>keepends=False</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.splitlines" title="Permalink to this definition">¶</a></dt> <dd><p>Return a list of the lines in the binary sequence, breaking at ASCII line boundaries. This method uses the <a class="reference internal" href="../glossary.html#term-universal-newlines"><span class="xref std std-term">universal newlines</span></a> approach to splitting lines. Line breaks are not included in the resulting list unless <em>keepends</em> is given and true.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'ab c</span><span class="se">\n\n</span><span class="s1">de fg</span><span class="se">\r</span><span class="s1">kl</span><span class="se">\r\n</span><span class="s1">'</span><span class="o">.</span><span class="n">splitlines</span><span class="p">()</span> <span class="go">[b'ab c', b'', b'de fg', b'kl']</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s1">'ab c</span><span class="se">\n\n</span><span class="s1">de fg</span><span class="se">\r</span><span class="s1">kl</span><span class="se">\r\n</span><span class="s1">'</span><span class="o">.</span><span class="n">splitlines</span><span class="p">(</span><span class="n">keepends</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="go">[b'ab c\n', b'\n', b'de fg\r', b'kl\r\n']</span> </pre></div> </div> <p>Unlike <a class="reference internal" href="#bytes.split" title="bytes.split"><code class="xref py py-meth docutils literal notranslate"><span class="pre">split()</span></code></a> when a delimiter string <em>sep</em> is given, this method returns an empty list for the empty string, and a terminal line break does not result in an extra line:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s2">""</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">),</span> <span class="sa">b</span><span class="s2">"Two lines</span><span class="se">\n</span><span class="s2">"</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span> <span class="go">([b''], [b'Two lines', b''])</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s2">""</span><span class="o">.</span><span class="n">splitlines</span><span class="p">(),</span> <span class="sa">b</span><span class="s2">"One line</span><span class="se">\n</span><span class="s2">"</span><span class="o">.</span><span class="n">splitlines</span><span class="p">()</span> <span class="go">([], [b'One line'])</span> </pre></div> </div> </dd></dl> <dl class="method"> <dt id="bytes.swapcase"> <code class="descclassname">bytes.</code><code class="descname">swapcase</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.swapcase" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.swapcase"> <code class="descclassname">bytearray.</code><code class="descname">swapcase</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.swapcase" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with all the lowercase ASCII characters converted to their corresponding uppercase counterpart and vice-versa.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello World'</span><span class="o">.</span><span class="n">swapcase</span><span class="p">()</span> <span class="go">b'hELLO wORLD'</span> </pre></div> </div> <p>Lowercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyz'</span></code>. Uppercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>.</p> <p>Unlike <a class="reference internal" href="#str.swapcase" title="str.swapcase"><code class="xref py py-func docutils literal notranslate"><span class="pre">str.swapcase()</span></code></a>, it is always the case that <code class="docutils literal notranslate"><span class="pre">bin.swapcase().swapcase()</span> <span class="pre">==</span> <span class="pre">bin</span></code> for the binary versions. Case conversions are symmetrical in ASCII, even though that is not generally true for arbitrary Unicode code points.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.title"> <code class="descclassname">bytes.</code><code class="descname">title</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.title" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.title"> <code class="descclassname">bytearray.</code><code class="descname">title</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.title" title="Permalink to this definition">¶</a></dt> <dd><p>Return a titlecased version of the binary sequence where words start with an uppercase ASCII character and the remaining characters are lowercase. Uncased byte values are left unmodified.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello world'</span><span class="o">.</span><span class="n">title</span><span class="p">()</span> <span class="go">b'Hello World'</span> </pre></div> </div> <p>Lowercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyz'</span></code>. Uppercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>. All other byte values are uncased.</p> <p>The algorithm uses a simple language-independent definition of a word as groups of consecutive letters. The definition works in many contexts but it means that apostrophes in contractions and possessives form word boundaries, which may not be the desired result:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s2">"they're bill's friends from the UK"</span><span class="o">.</span><span class="n">title</span><span class="p">()</span> <span class="go">b"They'Re Bill'S Friends From The Uk"</span> </pre></div> </div> <p>A workaround for apostrophes can be constructed using regular expressions:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">re</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">titlecase</span><span class="p">(</span><span class="n">s</span><span class="p">):</span> <span class="gp">... </span> <span class="k">return</span> <span class="n">re</span><span class="o">.</span><span class="n">sub</span><span class="p">(</span><span class="sa">rb</span><span class="s2">"[A-Za-z]+('[A-Za-z]+)?"</span><span class="p">,</span> <span class="gp">... </span> <span class="k">lambda</span> <span class="n">mo</span><span class="p">:</span> <span class="n">mo</span><span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="mi">0</span><span class="p">)[</span><span class="mi">0</span><span class="p">:</span><span class="mi">1</span><span class="p">]</span><span class="o">.</span><span class="n">upper</span><span class="p">()</span> <span class="o">+</span> <span class="gp">... </span> <span class="n">mo</span><span class="o">.</span><span class="n">group</span><span class="p">(</span><span class="mi">0</span><span class="p">)[</span><span class="mi">1</span><span class="p">:]</span><span class="o">.</span><span class="n">lower</span><span class="p">(),</span> <span class="gp">... </span> <span class="n">s</span><span class="p">)</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">titlecase</span><span class="p">(</span><span class="sa">b</span><span class="s2">"they're bill's friends."</span><span class="p">)</span> <span class="go">b"They're Bill's Friends."</span> </pre></div> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.upper"> <code class="descclassname">bytes.</code><code class="descname">upper</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytes.upper" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.upper"> <code class="descclassname">bytearray.</code><code class="descname">upper</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.upper" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence with all the lowercase ASCII characters converted to their corresponding uppercase counterpart.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s1">'Hello World'</span><span class="o">.</span><span class="n">upper</span><span class="p">()</span> <span class="go">b'HELLO WORLD'</span> </pre></div> </div> <p>Lowercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'abcdefghijklmnopqrstuvwxyz'</span></code>. Uppercase ASCII characters are those byte values in the sequence <code class="docutils literal notranslate"><span class="pre">b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'</span></code>.</p> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> <dl class="method"> <dt id="bytes.zfill"> <code class="descclassname">bytes.</code><code class="descname">zfill</code><span class="sig-paren">(</span><em>width</em><span class="sig-paren">)</span><a class="headerlink" href="#bytes.zfill" title="Permalink to this definition">¶</a></dt> <dt id="bytearray.zfill"> <code class="descclassname">bytearray.</code><code class="descname">zfill</code><span class="sig-paren">(</span><em>width</em><span class="sig-paren">)</span><a class="headerlink" href="#bytearray.zfill" title="Permalink to this definition">¶</a></dt> <dd><p>Return a copy of the sequence left filled with ASCII <code class="docutils literal notranslate"><span class="pre">b'0'</span></code> digits to make a sequence of length <em>width</em>. A leading sign prefix (<code class="docutils literal notranslate"><span class="pre">b'+'</span></code>/ <code class="docutils literal notranslate"><span class="pre">b'-'</span></code> is handled by inserting the padding <em>after</em> the sign character rather than before. For <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> objects, the original sequence is returned if <em>width</em> is less than or equal to <code class="docutils literal notranslate"><span class="pre">len(seq)</span></code>.</p> <p>For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="sa">b</span><span class="s2">"42"</span><span class="o">.</span><span class="n">zfill</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="go">b'00042'</span> <span class="gp">>>> </span><span class="sa">b</span><span class="s2">"-42"</span><span class="o">.</span><span class="n">zfill</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span> <span class="go">b'-0042'</span> </pre></div> </div> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> </dd></dl> </div> <div class="section" id="printf-style-bytes-formatting"> <span id="bytes-formatting"></span><h3>4.8.4. <code class="docutils literal notranslate"><span class="pre">printf</span></code>-style Bytes Formatting<a class="headerlink" href="#printf-style-bytes-formatting" title="Permalink to this headline">¶</a></h3> <div class="admonition note" id="index-41"> <p class="first admonition-title">Note</p> <p class="last">The formatting operations described here exhibit a variety of quirks that lead to a number of common errors (such as failing to display tuples and dictionaries correctly). If the value being printed may be a tuple or dictionary, wrap it in a tuple.</p> </div> <p>Bytes objects (<code class="docutils literal notranslate"><span class="pre">bytes</span></code>/<code class="docutils literal notranslate"><span class="pre">bytearray</span></code>) have one unique built-in operation: the <code class="docutils literal notranslate"><span class="pre">%</span></code> operator (modulo). This is also known as the bytes <em>formatting</em> or <em>interpolation</em> operator. Given <code class="docutils literal notranslate"><span class="pre">format</span> <span class="pre">%</span> <span class="pre">values</span></code> (where <em>format</em> is a bytes object), <code class="docutils literal notranslate"><span class="pre">%</span></code> conversion specifications in <em>format</em> are replaced with zero or more elements of <em>values</em>. The effect is similar to using the <code class="xref c c-func docutils literal notranslate"><span class="pre">sprintf()</span></code> in the C language.</p> <p>If <em>format</em> requires a single argument, <em>values</em> may be a single non-tuple object. <a class="footnote-reference" href="#id16" id="id11">[5]</a> Otherwise, <em>values</em> must be a tuple with exactly the number of items specified by the format bytes object, or a single mapping object (for example, a dictionary).</p> <p>A conversion specifier contains two or more characters and has the following components, which must occur in this order:</p> <ol class="arabic simple"> <li>The <code class="docutils literal notranslate"><span class="pre">'%'</span></code> character, which marks the start of the specifier.</li> <li>Mapping key (optional), consisting of a parenthesised sequence of characters (for example, <code class="docutils literal notranslate"><span class="pre">(somename)</span></code>).</li> <li>Conversion flags (optional), which affect the result of some conversion types.</li> <li>Minimum field width (optional). If specified as an <code class="docutils literal notranslate"><span class="pre">'*'</span></code> (asterisk), the actual width is read from the next element of the tuple in <em>values</em>, and the object to convert comes after the minimum field width and optional precision.</li> <li>Precision (optional), given as a <code class="docutils literal notranslate"><span class="pre">'.'</span></code> (dot) followed by the precision. If specified as <code class="docutils literal notranslate"><span class="pre">'*'</span></code> (an asterisk), the actual precision is read from the next element of the tuple in <em>values</em>, and the value to convert comes after the precision.</li> <li>Length modifier (optional).</li> <li>Conversion type.</li> </ol> <p>When the right argument is a dictionary (or other mapping type), then the formats in the bytes object <em>must</em> include a parenthesised mapping key into that dictionary inserted immediately after the <code class="docutils literal notranslate"><span class="pre">'%'</span></code> character. The mapping key selects the value to be formatted from the mapping. For example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="sa">b</span><span class="s1">'</span><span class="si">%(language)s</span><span class="s1"> has </span><span class="si">%(number)03d</span><span class="s1"> quote types.'</span> <span class="o">%</span> <span class="gp">... </span> <span class="p">{</span><span class="sa">b</span><span class="s1">'language'</span><span class="p">:</span> <span class="sa">b</span><span class="s2">"Python"</span><span class="p">,</span> <span class="sa">b</span><span class="s2">"number"</span><span class="p">:</span> <span class="mi">2</span><span class="p">})</span> <span class="go">b'Python has 002 quote types.'</span> </pre></div> </div> <p>In this case no <code class="docutils literal notranslate"><span class="pre">*</span></code> specifiers may occur in a format (since they require a sequential parameter list).</p> <p>The conversion flag characters are:</p> <table border="1" class="docutils"> <colgroup> <col width="12%" /> <col width="88%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Flag</th> <th class="head">Meaning</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'#'</span></code></td> <td>The value conversion will use the “alternate form” (where defined below).</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'0'</span></code></td> <td>The conversion will be zero padded for numeric values.</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'-'</span></code></td> <td>The converted value is left adjusted (overrides the <code class="docutils literal notranslate"><span class="pre">'0'</span></code> conversion if both are given).</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'</span> <span class="pre">'</span></code></td> <td>(a space) A blank should be left before a positive number (or empty string) produced by a signed conversion.</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'+'</span></code></td> <td>A sign character (<code class="docutils literal notranslate"><span class="pre">'+'</span></code> or <code class="docutils literal notranslate"><span class="pre">'-'</span></code>) will precede the conversion (overrides a “space” flag).</td> </tr> </tbody> </table> <p>A length modifier (<code class="docutils literal notranslate"><span class="pre">h</span></code>, <code class="docutils literal notranslate"><span class="pre">l</span></code>, or <code class="docutils literal notranslate"><span class="pre">L</span></code>) may be present, but is ignored as it is not necessary for Python – so e.g. <code class="docutils literal notranslate"><span class="pre">%ld</span></code> is identical to <code class="docutils literal notranslate"><span class="pre">%d</span></code>.</p> <p>The conversion types are:</p> <table border="1" class="docutils"> <colgroup> <col width="17%" /> <col width="74%" /> <col width="10%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Conversion</th> <th class="head">Meaning</th> <th class="head">Notes</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'d'</span></code></td> <td>Signed integer decimal.</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'i'</span></code></td> <td>Signed integer decimal.</td> <td> </td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'o'</span></code></td> <td>Signed octal value.</td> <td>(1)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'u'</span></code></td> <td>Obsolete type – it is identical to <code class="docutils literal notranslate"><span class="pre">'d'</span></code>.</td> <td>(8)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'x'</span></code></td> <td>Signed hexadecimal (lowercase).</td> <td>(2)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'X'</span></code></td> <td>Signed hexadecimal (uppercase).</td> <td>(2)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'e'</span></code></td> <td>Floating point exponential format (lowercase).</td> <td>(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'E'</span></code></td> <td>Floating point exponential format (uppercase).</td> <td>(3)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'f'</span></code></td> <td>Floating point decimal format.</td> <td>(3)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'F'</span></code></td> <td>Floating point decimal format.</td> <td>(3)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'g'</span></code></td> <td>Floating point format. Uses lowercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.</td> <td>(4)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'G'</span></code></td> <td>Floating point format. Uses uppercase exponential format if exponent is less than -4 or not less than precision, decimal format otherwise.</td> <td>(4)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'c'</span></code></td> <td>Single byte (accepts integer or single byte objects).</td> <td> </td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'b'</span></code></td> <td>Bytes (any object that follows the <a class="reference internal" href="../c-api/buffer.html#bufferobjects"><span class="std std-ref">buffer protocol</span></a> or has <a class="reference internal" href="../reference/datamodel.html#object.__bytes__" title="object.__bytes__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__bytes__()</span></code></a>).</td> <td>(5)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'s'</span></code></td> <td><code class="docutils literal notranslate"><span class="pre">'s'</span></code> is an alias for <code class="docutils literal notranslate"><span class="pre">'b'</span></code> and should only be used for Python2/3 code bases.</td> <td>(6)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'a'</span></code></td> <td>Bytes (converts any Python object using <code class="docutils literal notranslate"><span class="pre">repr(obj).encode('ascii','backslashreplace)</span></code>).</td> <td>(5)</td> </tr> <tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'r'</span></code></td> <td><code class="docutils literal notranslate"><span class="pre">'r'</span></code> is an alias for <code class="docutils literal notranslate"><span class="pre">'a'</span></code> and should only be used for Python2/3 code bases.</td> <td>(7)</td> </tr> <tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'%'</span></code></td> <td>No argument is converted, results in a <code class="docutils literal notranslate"><span class="pre">'%'</span></code> character in the result.</td> <td> </td> </tr> </tbody> </table> <p>Notes:</p> <ol class="arabic"> <li><p class="first">The alternate form causes a leading octal specifier (<code class="docutils literal notranslate"><span class="pre">'0o'</span></code>) to be inserted before the first digit.</p> </li> <li><p class="first">The alternate form causes a leading <code class="docutils literal notranslate"><span class="pre">'0x'</span></code> or <code class="docutils literal notranslate"><span class="pre">'0X'</span></code> (depending on whether the <code class="docutils literal notranslate"><span class="pre">'x'</span></code> or <code class="docutils literal notranslate"><span class="pre">'X'</span></code> format was used) to be inserted before the first digit.</p> </li> <li><p class="first">The alternate form causes the result to always contain a decimal point, even if no digits follow it.</p> <p>The precision determines the number of digits after the decimal point and defaults to 6.</p> </li> <li><p class="first">The alternate form causes the result to always contain a decimal point, and trailing zeroes are not removed as they would otherwise be.</p> <p>The precision determines the number of significant digits before and after the decimal point and defaults to 6.</p> </li> <li><p class="first">If precision is <code class="docutils literal notranslate"><span class="pre">N</span></code>, the output is truncated to <code class="docutils literal notranslate"><span class="pre">N</span></code> characters.</p> </li> <li><p class="first"><code class="docutils literal notranslate"><span class="pre">b'%s'</span></code> is deprecated, but will not be removed during the 3.x series.</p> </li> <li><p class="first"><code class="docutils literal notranslate"><span class="pre">b'%r'</span></code> is deprecated, but will not be removed during the 3.x series.</p> </li> <li><p class="first">See <span class="target" id="index-42"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0237"><strong>PEP 237</strong></a>.</p> </li> </ol> <div class="admonition note"> <p class="first admonition-title">Note</p> <p class="last">The bytearray version of this method does <em>not</em> operate in place - it always produces a new object, even if no changes were made.</p> </div> <div class="admonition seealso"> <p class="first admonition-title">See also</p> <p class="last"><span class="target" id="index-43"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0461"><strong>PEP 461</strong></a> - Adding % formatting to bytes and bytearray</p> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </div> <div class="section" id="memory-views"> <span id="typememoryview"></span><h3>4.8.5. Memory Views<a class="headerlink" href="#memory-views" title="Permalink to this headline">¶</a></h3> <p><a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> objects allow Python code to access the internal data of an object that supports the <a class="reference internal" href="../c-api/buffer.html#bufferobjects"><span class="std std-ref">buffer protocol</span></a> without copying.</p> <dl class="class"> <dt id="memoryview"> <em class="property">class </em><code class="descname">memoryview</code><span class="sig-paren">(</span><em>obj</em><span class="sig-paren">)</span><a class="headerlink" href="#memoryview" title="Permalink to this definition">¶</a></dt> <dd><p>Create a <a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> that references <em>obj</em>. <em>obj</em> must support the buffer protocol. Built-in objects that support the buffer protocol include <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> and <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>.</p> <p>A <a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> has the notion of an <em>element</em>, which is the atomic memory unit handled by the originating object <em>obj</em>. For many simple types such as <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> and <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a>, an element is a single byte, but other types such as <a class="reference internal" href="array.html#array.array" title="array.array"><code class="xref py py-class docutils literal notranslate"><span class="pre">array.array</span></code></a> may have bigger elements.</p> <p><code class="docutils literal notranslate"><span class="pre">len(view)</span></code> is equal to the length of <a class="reference internal" href="#memoryview.tolist" title="memoryview.tolist"><code class="xref py py-class docutils literal notranslate"><span class="pre">tolist</span></code></a>. If <code class="docutils literal notranslate"><span class="pre">view.ndim</span> <span class="pre">=</span> <span class="pre">0</span></code>, the length is 1. If <code class="docutils literal notranslate"><span class="pre">view.ndim</span> <span class="pre">=</span> <span class="pre">1</span></code>, the length is equal to the number of elements in the view. For higher dimensions, the length is equal to the length of the nested list representation of the view. The <a class="reference internal" href="#memoryview.itemsize" title="memoryview.itemsize"><code class="xref py py-class docutils literal notranslate"><span class="pre">itemsize</span></code></a> attribute will give you the number of bytes in a single element.</p> <p>A <a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> supports slicing and indexing to expose its data. One-dimensional slicing will result in a subview:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">v</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abcefg'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="go">98</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="go">103</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p">]</span> <span class="go"><memory at 0x7f3ddc9f4350></span> <span class="gp">>>> </span><span class="nb">bytes</span><span class="p">(</span><span class="n">v</span><span class="p">[</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p">])</span> <span class="go">b'bce'</span> </pre></div> </div> <p>If <a class="reference internal" href="#memoryview.format" title="memoryview.format"><code class="xref py py-class docutils literal notranslate"><span class="pre">format</span></code></a> is one of the native format specifiers from the <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> module, indexing with an integer or a tuple of integers is also supported and returns a single <em>element</em> with the correct type. One-dimensional memoryviews can be indexed with an integer or a one-integer tuple. Multi-dimensional memoryviews can be indexed with tuples of exactly <em>ndim</em> integers where <em>ndim</em> is the number of dimensions. Zero-dimensional memoryviews can be indexed with the empty tuple.</p> <p>Here is an example with a non-byte format:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">array</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'l'</span><span class="p">,</span> <span class="p">[</span><span class="o">-</span><span class="mi">11111111</span><span class="p">,</span> <span class="mi">22222222</span><span class="p">,</span> <span class="o">-</span><span class="mi">33333333</span><span class="p">,</span> <span class="mi">44444444</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="go">-11111111</span> <span class="gp">>>> </span><span class="n">m</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]</span> <span class="go">44444444</span> <span class="gp">>>> </span><span class="n">m</span><span class="p">[::</span><span class="mi">2</span><span class="p">]</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">[-11111111, -33333333]</span> </pre></div> </div> <p>If the underlying object is writable, the memoryview supports one-dimensional slice assignment. Resizing is not allowed:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">data</span> <span class="o">=</span> <span class="nb">bytearray</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abcefg'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">v</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">data</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">v</span><span class="o">.</span><span class="n">readonly</span> <span class="go">False</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="nb">ord</span><span class="p">(</span><span class="sa">b</span><span class="s1">'z'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">data</span> <span class="go">bytearray(b'zbcefg')</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="mi">1</span><span class="p">:</span><span class="mi">4</span><span class="p">]</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">'123'</span> <span class="gp">>>> </span><span class="n">data</span> <span class="go">bytearray(b'z123fg')</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="mi">2</span><span class="p">:</span><span class="mi">3</span><span class="p">]</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">'spam'</span> <span class="gt">Traceback (most recent call last):</span> File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n"><module></span> <span class="gr">ValueError</span>: <span class="n">memoryview assignment: lvalue and rvalue have different structures</span> <span class="gp">>>> </span><span class="n">v</span><span class="p">[</span><span class="mi">2</span><span class="p">:</span><span class="mi">6</span><span class="p">]</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">'spam'</span> <span class="gp">>>> </span><span class="n">data</span> <span class="go">bytearray(b'z1spam')</span> </pre></div> </div> <p>One-dimensional memoryviews of hashable (read-only) types with formats ‘B’, ‘b’ or ‘c’ are also hashable. The hash is defined as <code class="docutils literal notranslate"><span class="pre">hash(m)</span> <span class="pre">==</span> <span class="pre">hash(m.tobytes())</span></code>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">v</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abcefg'</span><span class="p">)</span> <span class="gp">>>> </span><span class="nb">hash</span><span class="p">(</span><span class="n">v</span><span class="p">)</span> <span class="o">==</span> <span class="nb">hash</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abcefg'</span><span class="p">)</span> <span class="go">True</span> <span class="gp">>>> </span><span class="nb">hash</span><span class="p">(</span><span class="n">v</span><span class="p">[</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">])</span> <span class="o">==</span> <span class="nb">hash</span><span class="p">(</span><span class="sa">b</span><span class="s1">'ce'</span><span class="p">)</span> <span class="go">True</span> <span class="gp">>>> </span><span class="nb">hash</span><span class="p">(</span><span class="n">v</span><span class="p">[::</span><span class="o">-</span><span class="mi">2</span><span class="p">])</span> <span class="o">==</span> <span class="nb">hash</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abcefg'</span><span class="p">[::</span><span class="o">-</span><span class="mi">2</span><span class="p">])</span> <span class="go">True</span> </pre></div> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>One-dimensional memoryviews can now be sliced. One-dimensional memoryviews with formats ‘B’, ‘b’ or ‘c’ are now hashable.</p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.4: </span>memoryview is now registered automatically with <a class="reference internal" href="collections.abc.html#collections.abc.Sequence" title="collections.abc.Sequence"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.abc.Sequence</span></code></a></p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.5: </span>memoryviews can now be indexed with tuple of integers.</p> </div> <p><a class="reference internal" href="#memoryview" title="memoryview"><code class="xref py py-class docutils literal notranslate"><span class="pre">memoryview</span></code></a> has several methods:</p> <dl class="method"> <dt id="memoryview.__eq__"> <code class="descname">__eq__</code><span class="sig-paren">(</span><em>exporter</em><span class="sig-paren">)</span><a class="headerlink" href="#memoryview.__eq__" title="Permalink to this definition">¶</a></dt> <dd><p>A memoryview and a <span class="target" id="index-44"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-3118"><strong>PEP 3118</strong></a> exporter are equal if their shapes are equivalent and if all corresponding values are equal when the operands’ respective format codes are interpreted using <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> syntax.</p> <p>For the subset of <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> format strings currently supported by <a class="reference internal" href="#memoryview.tolist" title="memoryview.tolist"><code class="xref py py-meth docutils literal notranslate"><span class="pre">tolist()</span></code></a>, <code class="docutils literal notranslate"><span class="pre">v</span></code> and <code class="docutils literal notranslate"><span class="pre">w</span></code> are equal if <code class="docutils literal notranslate"><span class="pre">v.tolist()</span> <span class="pre">==</span> <span class="pre">w.tolist()</span></code>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">array</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'I'</span><span class="p">,</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'d'</span><span class="p">,</span> <span class="p">[</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">2.0</span><span class="p">,</span> <span class="mf">3.0</span><span class="p">,</span> <span class="mf">4.0</span><span class="p">,</span> <span class="mf">5.0</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'b'</span><span class="p">,</span> <span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">b</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">==</span> <span class="n">a</span> <span class="o">==</span> <span class="n">y</span> <span class="o">==</span> <span class="n">b</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">x</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="o">==</span> <span class="n">a</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="o">==</span> <span class="n">y</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="o">==</span> <span class="n">b</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">z</span> <span class="o">=</span> <span class="n">y</span><span class="p">[::</span><span class="o">-</span><span class="mi">2</span><span class="p">]</span> <span class="gp">>>> </span><span class="n">z</span> <span class="o">==</span> <span class="n">c</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">z</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="o">==</span> <span class="n">c</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">True</span> </pre></div> </div> <p>If either format string is not supported by the <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> module, then the objects will always compare as unequal (even if the format strings and buffer contents are identical):</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">ctypes</span> <span class="k">import</span> <span class="n">BigEndianStructure</span><span class="p">,</span> <span class="n">c_long</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">BEPoint</span><span class="p">(</span><span class="n">BigEndianStructure</span><span class="p">):</span> <span class="gp">... </span> <span class="n">_fields_</span> <span class="o">=</span> <span class="p">[(</span><span class="s2">"x"</span><span class="p">,</span> <span class="n">c_long</span><span class="p">),</span> <span class="p">(</span><span class="s2">"y"</span><span class="p">,</span> <span class="n">c_long</span><span class="p">)]</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">point</span> <span class="o">=</span> <span class="n">BEPoint</span><span class="p">(</span><span class="mi">100</span><span class="p">,</span> <span class="mi">200</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">point</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">point</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">==</span> <span class="n">point</span> <span class="go">False</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">==</span> <span class="n">b</span> <span class="go">False</span> </pre></div> </div> <p>Note that, as with floating point numbers, <code class="docutils literal notranslate"><span class="pre">v</span> <span class="pre">is</span> <span class="pre">w</span></code> does <em>not</em> imply <code class="docutils literal notranslate"><span class="pre">v</span> <span class="pre">==</span> <span class="pre">w</span></code> for memoryview objects.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>Previous versions compared the raw memory disregarding the item format and the logical array structure.</p> </div> </dd></dl> <dl class="method"> <dt id="memoryview.tobytes"> <code class="descname">tobytes</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#memoryview.tobytes" title="Permalink to this definition">¶</a></dt> <dd><p>Return the data in the buffer as a bytestring. This is equivalent to calling the <a class="reference internal" href="#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> constructor on the memoryview.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s2">"abc"</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">tobytes</span><span class="p">()</span> <span class="go">b'abc'</span> <span class="gp">>>> </span><span class="nb">bytes</span><span class="p">(</span><span class="n">m</span><span class="p">)</span> <span class="go">b'abc'</span> </pre></div> </div> <p>For non-contiguous arrays the result is equal to the flattened list representation with all elements converted to bytes. <a class="reference internal" href="#memoryview.tobytes" title="memoryview.tobytes"><code class="xref py py-meth docutils literal notranslate"><span class="pre">tobytes()</span></code></a> supports all format strings, including those that are not in <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> module syntax.</p> </dd></dl> <dl class="method"> <dt id="memoryview.hex"> <code class="descname">hex</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#memoryview.hex" title="Permalink to this definition">¶</a></dt> <dd><p>Return a string object containing two hexadecimal digits for each byte in the buffer.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s2">"abc"</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">hex</span><span class="p">()</span> <span class="go">'616263'</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.5.</span></p> </div> </dd></dl> <dl class="method"> <dt id="memoryview.tolist"> <code class="descname">tolist</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#memoryview.tolist" title="Permalink to this definition">¶</a></dt> <dd><p>Return the data in the buffer as a list of elements.</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abc'</span><span class="p">)</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">[97, 98, 99]</span> <span class="gp">>>> </span><span class="kn">import</span> <span class="nn">array</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'d'</span><span class="p">,</span> <span class="p">[</span><span class="mf">1.1</span><span class="p">,</span> <span class="mf">2.2</span><span class="p">,</span> <span class="mf">3.3</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">[1.1, 2.2, 3.3]</span> </pre></div> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span><a class="reference internal" href="#memoryview.tolist" title="memoryview.tolist"><code class="xref py py-meth docutils literal notranslate"><span class="pre">tolist()</span></code></a> now supports all single character native formats in <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> module syntax as well as multi-dimensional representations.</p> </div> </dd></dl> <dl class="method"> <dt id="memoryview.release"> <code class="descname">release</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#memoryview.release" title="Permalink to this definition">¶</a></dt> <dd><p>Release the underlying buffer exposed by the memoryview object. Many objects take special actions when a view is held on them (for example, a <a class="reference internal" href="#bytearray" title="bytearray"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytearray</span></code></a> would temporarily forbid resizing); therefore, calling release() is handy to remove these restrictions (and free any dangling resources) as soon as possible.</p> <p>After this method has been called, any further operation on the view raises a <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-class docutils literal notranslate"><span class="pre">ValueError</span></code></a> (except <a class="reference internal" href="#memoryview.release" title="memoryview.release"><code class="xref py py-meth docutils literal notranslate"><span class="pre">release()</span></code></a> itself which can be called multiple times):</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abc'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">release</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="gt">Traceback (most recent call last):</span> File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n"><module></span> <span class="gr">ValueError</span>: <span class="n">operation forbidden on released memoryview object</span> </pre></div> </div> <p>The context management protocol can be used for a similar effect, using the <code class="docutils literal notranslate"><span class="pre">with</span></code> statement:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">with</span> <span class="nb">memoryview</span><span class="p">(</span><span class="sa">b</span><span class="s1">'abc'</span><span class="p">)</span> <span class="k">as</span> <span class="n">m</span><span class="p">:</span> <span class="gp">... </span> <span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="gp">...</span> <span class="go">97</span> <span class="gp">>>> </span><span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="gt">Traceback (most recent call last):</span> File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n"><module></span> <span class="gr">ValueError</span>: <span class="n">operation forbidden on released memoryview object</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.2.</span></p> </div> </dd></dl> <dl class="method"> <dt id="memoryview.cast"> <code class="descname">cast</code><span class="sig-paren">(</span><em>format</em><span class="optional">[</span>, <em>shape</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#memoryview.cast" title="Permalink to this definition">¶</a></dt> <dd><p>Cast a memoryview to a new format or shape. <em>shape</em> defaults to <code class="docutils literal notranslate"><span class="pre">[byte_length//new_itemsize]</span></code>, which means that the result view will be one-dimensional. The return value is a new memoryview, but the buffer itself is not copied. Supported casts are 1D -> C-<a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a> and C-contiguous -> 1D.</p> <p>The destination format is restricted to a single element native format in <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> syntax. One of the formats must be a byte format (‘B’, ‘b’ or ‘c’). The byte length of the result must be the same as the original length.</p> <p>Cast 1D/long to 1D/unsigned bytes:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">array</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'l'</span><span class="p">,</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">x</span><span class="o">.</span><span class="n">format</span> <span class="go">'l'</span> <span class="gp">>>> </span><span class="n">x</span><span class="o">.</span><span class="n">itemsize</span> <span class="go">8</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">x</span><span class="p">)</span> <span class="go">3</span> <span class="gp">>>> </span><span class="n">x</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">24</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">'B'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">format</span> <span class="go">'B'</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">itemsize</span> <span class="go">1</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">y</span><span class="p">)</span> <span class="go">24</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">24</span> </pre></div> </div> <p>Cast 1D/unsigned bytes to 1D/char:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="nb">bytearray</span><span class="p">(</span><span class="sa">b</span><span class="s1">'zyz'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">b</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">x</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">'a'</span> <span class="gt">Traceback (most recent call last):</span> File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n"><module></span> <span class="gr">ValueError</span>: <span class="n">memoryview: invalid value for format "B"</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">'c'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">y</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">'a'</span> <span class="gp">>>> </span><span class="n">b</span> <span class="go">bytearray(b'ayz')</span> </pre></div> </div> <p>Cast 1D/bytes to 3D/ints to 1D/signed char:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">struct</span> <span class="gp">>>> </span><span class="n">buf</span> <span class="o">=</span> <span class="n">struct</span><span class="o">.</span><span class="n">pack</span><span class="p">(</span><span class="s2">"i"</span><span class="o">*</span><span class="mi">12</span><span class="p">,</span> <span class="o">*</span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">12</span><span class="p">)))</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">'i'</span><span class="p">,</span> <span class="n">shape</span><span class="o">=</span><span class="p">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">[[[0, 1, 2], [3, 4, 5]], [[6, 7, 8], [9, 10, 11]]]</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">format</span> <span class="go">'i'</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">itemsize</span> <span class="go">4</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">y</span><span class="p">)</span> <span class="go">2</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">48</span> <span class="gp">>>> </span><span class="n">z</span> <span class="o">=</span> <span class="n">y</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">'b'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">z</span><span class="o">.</span><span class="n">format</span> <span class="go">'b'</span> <span class="gp">>>> </span><span class="n">z</span><span class="o">.</span><span class="n">itemsize</span> <span class="go">1</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">z</span><span class="p">)</span> <span class="go">48</span> <span class="gp">>>> </span><span class="n">z</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">48</span> </pre></div> </div> <p>Cast 1D/unsigned char to 2D/unsigned long:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">buf</span> <span class="o">=</span> <span class="n">struct</span><span class="o">.</span><span class="n">pack</span><span class="p">(</span><span class="s2">"L"</span><span class="o">*</span><span class="mi">6</span><span class="p">,</span> <span class="o">*</span><span class="nb">list</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">6</span><span class="p">)))</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">'L'</span><span class="p">,</span> <span class="n">shape</span><span class="o">=</span><span class="p">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">])</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">y</span><span class="p">)</span> <span class="go">2</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">48</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">[[0, 1, 2], [3, 4, 5]]</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.5: </span>The source format is no longer restricted when casting to a byte view.</p> </div> </dd></dl> <p>There are also several readonly attributes available:</p> <dl class="attribute"> <dt id="memoryview.obj"> <code class="descname">obj</code><a class="headerlink" href="#memoryview.obj" title="Permalink to this definition">¶</a></dt> <dd><p>The underlying object of the memoryview:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="nb">bytearray</span><span class="p">(</span><span class="sa">b</span><span class="s1">'xyz'</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">b</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">obj</span> <span class="ow">is</span> <span class="n">b</span> <span class="go">True</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.nbytes"> <code class="descname">nbytes</code><a class="headerlink" href="#memoryview.nbytes" title="Permalink to this definition">¶</a></dt> <dd><p><code class="docutils literal notranslate"><span class="pre">nbytes</span> <span class="pre">==</span> <span class="pre">product(shape)</span> <span class="pre">*</span> <span class="pre">itemsize</span> <span class="pre">==</span> <span class="pre">len(m.tobytes())</span></code>. This is the amount of space in bytes that the array would use in a contiguous representation. It is not necessarily equal to len(m):</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">array</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'i'</span><span class="p">,</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">m</span><span class="p">)</span> <span class="go">5</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">20</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">m</span><span class="p">[::</span><span class="mi">2</span><span class="p">]</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">y</span><span class="p">)</span> <span class="go">3</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">12</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">y</span><span class="o">.</span><span class="n">tobytes</span><span class="p">())</span> <span class="go">12</span> </pre></div> </div> <p>Multi-dimensional arrays:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">struct</span> <span class="gp">>>> </span><span class="n">buf</span> <span class="o">=</span> <span class="n">struct</span><span class="o">.</span><span class="n">pack</span><span class="p">(</span><span class="s2">"d"</span><span class="o">*</span><span class="mi">12</span><span class="p">,</span> <span class="o">*</span><span class="p">[</span><span class="mf">1.5</span><span class="o">*</span><span class="n">x</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">12</span><span class="p">)])</span> <span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">y</span> <span class="o">=</span> <span class="n">x</span><span class="o">.</span><span class="n">cast</span><span class="p">(</span><span class="s1">'d'</span><span class="p">,</span> <span class="n">shape</span><span class="o">=</span><span class="p">[</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">])</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">tolist</span><span class="p">()</span> <span class="go">[[0.0, 1.5, 3.0, 4.5], [6.0, 7.5, 9.0, 10.5], [12.0, 13.5, 15.0, 16.5]]</span> <span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">y</span><span class="p">)</span> <span class="go">3</span> <span class="gp">>>> </span><span class="n">y</span><span class="o">.</span><span class="n">nbytes</span> <span class="go">96</span> </pre></div> </div> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.readonly"> <code class="descname">readonly</code><a class="headerlink" href="#memoryview.readonly" title="Permalink to this definition">¶</a></dt> <dd><p>A bool indicating whether the memory is read only.</p> </dd></dl> <dl class="attribute"> <dt id="memoryview.format"> <code class="descname">format</code><a class="headerlink" href="#memoryview.format" title="Permalink to this definition">¶</a></dt> <dd><p>A string containing the format (in <a class="reference internal" href="struct.html#module-struct" title="struct: Interpret bytes as packed binary data."><code class="xref py py-mod docutils literal notranslate"><span class="pre">struct</span></code></a> module style) for each element in the view. A memoryview can be created from exporters with arbitrary format strings, but some methods (e.g. <a class="reference internal" href="#memoryview.tolist" title="memoryview.tolist"><code class="xref py py-meth docutils literal notranslate"><span class="pre">tolist()</span></code></a>) are restricted to native single element formats.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>format <code class="docutils literal notranslate"><span class="pre">'B'</span></code> is now handled according to the struct module syntax. This means that <code class="docutils literal notranslate"><span class="pre">memoryview(b'abc')[0]</span> <span class="pre">==</span> <span class="pre">b'abc'[0]</span> <span class="pre">==</span> <span class="pre">97</span></code>.</p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.itemsize"> <code class="descname">itemsize</code><a class="headerlink" href="#memoryview.itemsize" title="Permalink to this definition">¶</a></dt> <dd><p>The size in bytes of each element of the memoryview:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">array</span><span class="o">,</span> <span class="nn">struct</span> <span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="nb">memoryview</span><span class="p">(</span><span class="n">array</span><span class="o">.</span><span class="n">array</span><span class="p">(</span><span class="s1">'H'</span><span class="p">,</span> <span class="p">[</span><span class="mi">32000</span><span class="p">,</span> <span class="mi">32001</span><span class="p">,</span> <span class="mi">32002</span><span class="p">]))</span> <span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">itemsize</span> <span class="go">2</span> <span class="gp">>>> </span><span class="n">m</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="go">32000</span> <span class="gp">>>> </span><span class="n">struct</span><span class="o">.</span><span class="n">calcsize</span><span class="p">(</span><span class="s1">'H'</span><span class="p">)</span> <span class="o">==</span> <span class="n">m</span><span class="o">.</span><span class="n">itemsize</span> <span class="go">True</span> </pre></div> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.ndim"> <code class="descname">ndim</code><a class="headerlink" href="#memoryview.ndim" title="Permalink to this definition">¶</a></dt> <dd><p>An integer indicating how many dimensions of a multi-dimensional array the memory represents.</p> </dd></dl> <dl class="attribute"> <dt id="memoryview.shape"> <code class="descname">shape</code><a class="headerlink" href="#memoryview.shape" title="Permalink to this definition">¶</a></dt> <dd><p>A tuple of integers the length of <a class="reference internal" href="#memoryview.ndim" title="memoryview.ndim"><code class="xref py py-attr docutils literal notranslate"><span class="pre">ndim</span></code></a> giving the shape of the memory as an N-dimensional array.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>An empty tuple instead of <code class="docutils literal notranslate"><span class="pre">None</span></code> when ndim = 0.</p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.strides"> <code class="descname">strides</code><a class="headerlink" href="#memoryview.strides" title="Permalink to this definition">¶</a></dt> <dd><p>A tuple of integers the length of <a class="reference internal" href="#memoryview.ndim" title="memoryview.ndim"><code class="xref py py-attr docutils literal notranslate"><span class="pre">ndim</span></code></a> giving the size in bytes to access each element for each dimension of the array.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.3: </span>An empty tuple instead of <code class="docutils literal notranslate"><span class="pre">None</span></code> when ndim = 0.</p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.suboffsets"> <code class="descname">suboffsets</code><a class="headerlink" href="#memoryview.suboffsets" title="Permalink to this definition">¶</a></dt> <dd><p>Used internally for PIL-style arrays. The value is informational only.</p> </dd></dl> <dl class="attribute"> <dt id="memoryview.c_contiguous"> <code class="descname">c_contiguous</code><a class="headerlink" href="#memoryview.c_contiguous" title="Permalink to this definition">¶</a></dt> <dd><p>A bool indicating whether the memory is C-<a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a>.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.f_contiguous"> <code class="descname">f_contiguous</code><a class="headerlink" href="#memoryview.f_contiguous" title="Permalink to this definition">¶</a></dt> <dd><p>A bool indicating whether the memory is Fortran <a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a>.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="memoryview.contiguous"> <code class="descname">contiguous</code><a class="headerlink" href="#memoryview.contiguous" title="Permalink to this definition">¶</a></dt> <dd><p>A bool indicating whether the memory is <a class="reference internal" href="../glossary.html#term-contiguous"><span class="xref std std-term">contiguous</span></a>.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> </dd></dl> </div> </div> <div class="section" id="set-types-set-frozenset"> <span id="types-set"></span><h2>4.9. Set Types — <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a>, <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a><a class="headerlink" href="#set-types-set-frozenset" title="Permalink to this headline">¶</a></h2> <p id="index-45">A <em class="dfn">set</em> object is an unordered collection of distinct <a class="reference internal" href="../glossary.html#term-hashable"><span class="xref std std-term">hashable</span></a> objects. Common uses include membership testing, removing duplicates from a sequence, and computing mathematical operations such as intersection, union, difference, and symmetric difference. (For other containers see the built-in <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>, <a class="reference internal" href="#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a>, and <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a> classes, and the <a class="reference internal" href="collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate"><span class="pre">collections</span></code></a> module.)</p> <p>Like other collections, sets support <code class="docutils literal notranslate"><span class="pre">x</span> <span class="pre">in</span> <span class="pre">set</span></code>, <code class="docutils literal notranslate"><span class="pre">len(set)</span></code>, and <code class="docutils literal notranslate"><span class="pre">for</span> <span class="pre">x</span> <span class="pre">in</span> <span class="pre">set</span></code>. Being an unordered collection, sets do not record element position or order of insertion. Accordingly, sets do not support indexing, slicing, or other sequence-like behavior.</p> <p>There are currently two built-in set types, <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> and <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a>. The <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> type is mutable — the contents can be changed using methods like <code class="xref py py-meth docutils literal notranslate"><span class="pre">add()</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">remove()</span></code>. Since it is mutable, it has no hash value and cannot be used as either a dictionary key or as an element of another set. The <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> type is immutable and <a class="reference internal" href="../glossary.html#term-hashable"><span class="xref std std-term">hashable</span></a> — its contents cannot be altered after it is created; it can therefore be used as a dictionary key or as an element of another set.</p> <p>Non-empty sets (not frozensets) can be created by placing a comma-separated list of elements within braces, for example: <code class="docutils literal notranslate"><span class="pre">{'jack',</span> <span class="pre">'sjoerd'}</span></code>, in addition to the <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> constructor.</p> <p>The constructors for both classes work the same:</p> <dl class="class"> <dt id="set"> <em class="property">class </em><code class="descname">set</code><span class="sig-paren">(</span><span class="optional">[</span><em>iterable</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#set" title="Permalink to this definition">¶</a></dt> <dt id="frozenset"> <em class="property">class </em><code class="descname">frozenset</code><span class="sig-paren">(</span><span class="optional">[</span><em>iterable</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#frozenset" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new set or frozenset object whose elements are taken from <em>iterable</em>. The elements of a set must be <a class="reference internal" href="../glossary.html#term-hashable"><span class="xref std std-term">hashable</span></a>. To represent sets of sets, the inner sets must be <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> objects. If <em>iterable</em> is not specified, a new empty set is returned.</p> <p>Instances of <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> and <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> provide the following operations:</p> <dl class="describe"> <dt> <code class="descname">len(s)</code></dt> <dd><p>Return the number of elements in set <em>s</em> (cardinality of <em>s</em>).</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">x in s</code></dt> <dd><p>Test <em>x</em> for membership in <em>s</em>.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">x not in s</code></dt> <dd><p>Test <em>x</em> for non-membership in <em>s</em>.</p> </dd></dl> <dl class="method"> <dt id="frozenset.isdisjoint"> <code class="descname">isdisjoint</code><span class="sig-paren">(</span><em>other</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.isdisjoint" title="Permalink to this definition">¶</a></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the set has no elements in common with <em>other</em>. Sets are disjoint if and only if their intersection is the empty set.</p> </dd></dl> <dl class="method"> <dt id="frozenset.issubset"> <code class="descname">issubset</code><span class="sig-paren">(</span><em>other</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.issubset" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set <= other</code></dt> <dd><p>Test whether every element in the set is in <em>other</em>.</p> </dd></dl> <dl class="method"> <dt> <code class="descname">set < other</code></dt> <dd><p>Test whether the set is a proper subset of <em>other</em>, that is, <code class="docutils literal notranslate"><span class="pre">set</span> <span class="pre"><=</span> <span class="pre">other</span> <span class="pre">and</span> <span class="pre">set</span> <span class="pre">!=</span> <span class="pre">other</span></code>.</p> </dd></dl> <dl class="method"> <dt id="frozenset.issuperset"> <code class="descname">issuperset</code><span class="sig-paren">(</span><em>other</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.issuperset" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set >= other</code></dt> <dd><p>Test whether every element in <em>other</em> is in the set.</p> </dd></dl> <dl class="method"> <dt> <code class="descname">set > other</code></dt> <dd><p>Test whether the set is a proper superset of <em>other</em>, that is, <code class="docutils literal notranslate"><span class="pre">set</span> <span class="pre">>=</span> <span class="pre">other</span> <span class="pre">and</span> <span class="pre">set</span> <span class="pre">!=</span> <span class="pre">other</span></code>.</p> </dd></dl> <dl class="method"> <dt id="frozenset.union"> <code class="descname">union</code><span class="sig-paren">(</span><em>*others</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.union" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set | other | ...</code></dt> <dd><p>Return a new set with elements from the set and all others.</p> </dd></dl> <dl class="method"> <dt id="frozenset.intersection"> <code class="descname">intersection</code><span class="sig-paren">(</span><em>*others</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.intersection" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set & other & ...</code></dt> <dd><p>Return a new set with elements common to the set and all others.</p> </dd></dl> <dl class="method"> <dt id="frozenset.difference"> <code class="descname">difference</code><span class="sig-paren">(</span><em>*others</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.difference" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set - other - ...</code></dt> <dd><p>Return a new set with elements in the set that are not in the others.</p> </dd></dl> <dl class="method"> <dt id="frozenset.symmetric_difference"> <code class="descname">symmetric_difference</code><span class="sig-paren">(</span><em>other</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.symmetric_difference" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set ^ other</code></dt> <dd><p>Return a new set with elements in either the set or <em>other</em> but not both.</p> </dd></dl> <dl class="method"> <dt id="frozenset.copy"> <code class="descname">copy</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.copy" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new set with a shallow copy of <em>s</em>.</p> </dd></dl> <p>Note, the non-operator versions of <a class="reference internal" href="#frozenset.union" title="frozenset.union"><code class="xref py py-meth docutils literal notranslate"><span class="pre">union()</span></code></a>, <a class="reference internal" href="#frozenset.intersection" title="frozenset.intersection"><code class="xref py py-meth docutils literal notranslate"><span class="pre">intersection()</span></code></a>, <a class="reference internal" href="#frozenset.difference" title="frozenset.difference"><code class="xref py py-meth docutils literal notranslate"><span class="pre">difference()</span></code></a>, and <a class="reference internal" href="#frozenset.symmetric_difference" title="frozenset.symmetric_difference"><code class="xref py py-meth docutils literal notranslate"><span class="pre">symmetric_difference()</span></code></a>, <a class="reference internal" href="#frozenset.issubset" title="frozenset.issubset"><code class="xref py py-meth docutils literal notranslate"><span class="pre">issubset()</span></code></a>, and <a class="reference internal" href="#frozenset.issuperset" title="frozenset.issuperset"><code class="xref py py-meth docutils literal notranslate"><span class="pre">issuperset()</span></code></a> methods will accept any iterable as an argument. In contrast, their operator based counterparts require their arguments to be sets. This precludes error-prone constructions like <code class="docutils literal notranslate"><span class="pre">set('abc')</span> <span class="pre">&</span> <span class="pre">'cbs'</span></code> in favor of the more readable <code class="docutils literal notranslate"><span class="pre">set('abc').intersection('cbs')</span></code>.</p> <p>Both <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> and <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> support set to set comparisons. Two sets are equal if and only if every element of each set is contained in the other (each is a subset of the other). A set is less than another set if and only if the first set is a proper subset of the second set (is a subset, but is not equal). A set is greater than another set if and only if the first set is a proper superset of the second set (is a superset, but is not equal).</p> <p>Instances of <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> are compared to instances of <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> based on their members. For example, <code class="docutils literal notranslate"><span class="pre">set('abc')</span> <span class="pre">==</span> <span class="pre">frozenset('abc')</span></code> returns <code class="docutils literal notranslate"><span class="pre">True</span></code> and so does <code class="docutils literal notranslate"><span class="pre">set('abc')</span> <span class="pre">in</span> <span class="pre">set([frozenset('abc')])</span></code>.</p> <p>The subset and equality comparisons do not generalize to a total ordering function. For example, any two nonempty disjoint sets are not equal and are not subsets of each other, so <em>all</em> of the following return <code class="docutils literal notranslate"><span class="pre">False</span></code>: <code class="docutils literal notranslate"><span class="pre">a<b</span></code>, <code class="docutils literal notranslate"><span class="pre">a==b</span></code>, or <code class="docutils literal notranslate"><span class="pre">a>b</span></code>.</p> <p>Since sets only define partial ordering (subset relationships), the output of the <a class="reference internal" href="#list.sort" title="list.sort"><code class="xref py py-meth docutils literal notranslate"><span class="pre">list.sort()</span></code></a> method is undefined for lists of sets.</p> <p>Set elements, like dictionary keys, must be <a class="reference internal" href="../glossary.html#term-hashable"><span class="xref std std-term">hashable</span></a>.</p> <p>Binary operations that mix <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> instances with <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a> return the type of the first operand. For example: <code class="docutils literal notranslate"><span class="pre">frozenset('ab')</span> <span class="pre">|</span> <span class="pre">set('bc')</span></code> returns an instance of <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a>.</p> <p>The following table lists operations available for <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a> that do not apply to immutable instances of <a class="reference internal" href="#frozenset" title="frozenset"><code class="xref py py-class docutils literal notranslate"><span class="pre">frozenset</span></code></a>:</p> <dl class="method"> <dt id="frozenset.update"> <code class="descname">update</code><span class="sig-paren">(</span><em>*others</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.update" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set |= other | ...</code></dt> <dd><p>Update the set, adding elements from all others.</p> </dd></dl> <dl class="method"> <dt id="frozenset.intersection_update"> <code class="descname">intersection_update</code><span class="sig-paren">(</span><em>*others</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.intersection_update" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set &= other & ...</code></dt> <dd><p>Update the set, keeping only elements found in it and all others.</p> </dd></dl> <dl class="method"> <dt id="frozenset.difference_update"> <code class="descname">difference_update</code><span class="sig-paren">(</span><em>*others</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.difference_update" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set -= other | ...</code></dt> <dd><p>Update the set, removing elements found in others.</p> </dd></dl> <dl class="method"> <dt id="frozenset.symmetric_difference_update"> <code class="descname">symmetric_difference_update</code><span class="sig-paren">(</span><em>other</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.symmetric_difference_update" title="Permalink to this definition">¶</a></dt> <dt> <code class="descname">set ^= other</code></dt> <dd><p>Update the set, keeping only elements found in either set, but not in both.</p> </dd></dl> <dl class="method"> <dt id="frozenset.add"> <code class="descname">add</code><span class="sig-paren">(</span><em>elem</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.add" title="Permalink to this definition">¶</a></dt> <dd><p>Add element <em>elem</em> to the set.</p> </dd></dl> <dl class="method"> <dt id="frozenset.remove"> <code class="descname">remove</code><span class="sig-paren">(</span><em>elem</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.remove" title="Permalink to this definition">¶</a></dt> <dd><p>Remove element <em>elem</em> from the set. Raises <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> if <em>elem</em> is not contained in the set.</p> </dd></dl> <dl class="method"> <dt id="frozenset.discard"> <code class="descname">discard</code><span class="sig-paren">(</span><em>elem</em><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.discard" title="Permalink to this definition">¶</a></dt> <dd><p>Remove element <em>elem</em> from the set if it is present.</p> </dd></dl> <dl class="method"> <dt id="frozenset.pop"> <code class="descname">pop</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.pop" title="Permalink to this definition">¶</a></dt> <dd><p>Remove and return an arbitrary element from the set. Raises <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> if the set is empty.</p> </dd></dl> <dl class="method"> <dt id="frozenset.clear"> <code class="descname">clear</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#frozenset.clear" title="Permalink to this definition">¶</a></dt> <dd><p>Remove all elements from the set.</p> </dd></dl> <p>Note, the non-operator versions of the <a class="reference internal" href="#frozenset.update" title="frozenset.update"><code class="xref py py-meth docutils literal notranslate"><span class="pre">update()</span></code></a>, <a class="reference internal" href="#frozenset.intersection_update" title="frozenset.intersection_update"><code class="xref py py-meth docutils literal notranslate"><span class="pre">intersection_update()</span></code></a>, <a class="reference internal" href="#frozenset.difference_update" title="frozenset.difference_update"><code class="xref py py-meth docutils literal notranslate"><span class="pre">difference_update()</span></code></a>, and <a class="reference internal" href="#frozenset.symmetric_difference_update" title="frozenset.symmetric_difference_update"><code class="xref py py-meth docutils literal notranslate"><span class="pre">symmetric_difference_update()</span></code></a> methods will accept any iterable as an argument.</p> <p>Note, the <em>elem</em> argument to the <a class="reference internal" href="../reference/datamodel.html#object.__contains__" title="object.__contains__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__contains__()</span></code></a>, <a class="reference internal" href="#frozenset.remove" title="frozenset.remove"><code class="xref py py-meth docutils literal notranslate"><span class="pre">remove()</span></code></a>, and <a class="reference internal" href="#frozenset.discard" title="frozenset.discard"><code class="xref py py-meth docutils literal notranslate"><span class="pre">discard()</span></code></a> methods may be a set. To support searching for an equivalent frozenset, a temporary one is created from <em>elem</em>.</p> </dd></dl> </div> <div class="section" id="mapping-types-dict"> <span id="typesmapping"></span><h2>4.10. Mapping Types — <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a><a class="headerlink" href="#mapping-types-dict" title="Permalink to this headline">¶</a></h2> <p id="index-46">A <a class="reference internal" href="../glossary.html#term-mapping"><span class="xref std std-term">mapping</span></a> object maps <a class="reference internal" href="../glossary.html#term-hashable"><span class="xref std std-term">hashable</span></a> values to arbitrary objects. Mappings are mutable objects. There is currently only one standard mapping type, the <em class="dfn">dictionary</em>. (For other containers see the built-in <a class="reference internal" href="#list" title="list"><code class="xref py py-class docutils literal notranslate"><span class="pre">list</span></code></a>, <a class="reference internal" href="#set" title="set"><code class="xref py py-class docutils literal notranslate"><span class="pre">set</span></code></a>, and <a class="reference internal" href="#tuple" title="tuple"><code class="xref py py-class docutils literal notranslate"><span class="pre">tuple</span></code></a> classes, and the <a class="reference internal" href="collections.html#module-collections" title="collections: Container datatypes"><code class="xref py py-mod docutils literal notranslate"><span class="pre">collections</span></code></a> module.)</p> <p>A dictionary’s keys are <em>almost</em> arbitrary values. Values that are not <a class="reference internal" href="../glossary.html#term-hashable"><span class="xref std std-term">hashable</span></a>, that is, values containing lists, dictionaries or other mutable types (that are compared by value rather than by object identity) may not be used as keys. Numeric types used for keys obey the normal rules for numeric comparison: if two numbers compare equal (such as <code class="docutils literal notranslate"><span class="pre">1</span></code> and <code class="docutils literal notranslate"><span class="pre">1.0</span></code>) then they can be used interchangeably to index the same dictionary entry. (Note however, that since computers store floating-point numbers as approximations it is usually unwise to use them as dictionary keys.)</p> <p>Dictionaries can be created by placing a comma-separated list of <code class="docutils literal notranslate"><span class="pre">key:</span> <span class="pre">value</span></code> pairs within braces, for example: <code class="docutils literal notranslate"><span class="pre">{'jack':</span> <span class="pre">4098,</span> <span class="pre">'sjoerd':</span> <span class="pre">4127}</span></code> or <code class="docutils literal notranslate"><span class="pre">{4098:</span> <span class="pre">'jack',</span> <span class="pre">4127:</span> <span class="pre">'sjoerd'}</span></code>, or by the <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> constructor.</p> <dl class="class"> <dt id="dict"> <em class="property">class </em><code class="descname">dict</code><span class="sig-paren">(</span><em>**kwarg</em><span class="sig-paren">)</span><a class="headerlink" href="#dict" title="Permalink to this definition">¶</a></dt> <dt> <em class="property">class </em><code class="descname">dict</code><span class="sig-paren">(</span><em>mapping</em>, <em>**kwarg</em><span class="sig-paren">)</span></dt> <dt> <em class="property">class </em><code class="descname">dict</code><span class="sig-paren">(</span><em>iterable</em>, <em>**kwarg</em><span class="sig-paren">)</span></dt> <dd><p>Return a new dictionary initialized from an optional positional argument and a possibly empty set of keyword arguments.</p> <p>If no positional argument is given, an empty dictionary is created. If a positional argument is given and it is a mapping object, a dictionary is created with the same key-value pairs as the mapping object. Otherwise, the positional argument must be an <a class="reference internal" href="../glossary.html#term-iterable"><span class="xref std std-term">iterable</span></a> object. Each item in the iterable must itself be an iterable with exactly two objects. The first object of each item becomes a key in the new dictionary, and the second object the corresponding value. If a key occurs more than once, the last value for that key becomes the corresponding value in the new dictionary.</p> <p>If keyword arguments are given, the keyword arguments and their values are added to the dictionary created from the positional argument. If a key being added is already present, the value from the keyword argument replaces the value from the positional argument.</p> <p>To illustrate, the following examples all return a dictionary equal to <code class="docutils literal notranslate"><span class="pre">{"one":</span> <span class="pre">1,</span> <span class="pre">"two":</span> <span class="pre">2,</span> <span class="pre">"three":</span> <span class="pre">3}</span></code>:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">(</span><span class="n">one</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">two</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">three</span><span class="o">=</span><span class="mi">3</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">b</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'one'</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">'two'</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="s1">'three'</span><span class="p">:</span> <span class="mi">3</span><span class="p">}</span> <span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">(</span><span class="nb">zip</span><span class="p">([</span><span class="s1">'one'</span><span class="p">,</span> <span class="s1">'two'</span><span class="p">,</span> <span class="s1">'three'</span><span class="p">],</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]))</span> <span class="gp">>>> </span><span class="n">d</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">([(</span><span class="s1">'two'</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="s1">'one'</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="s1">'three'</span><span class="p">,</span> <span class="mi">3</span><span class="p">)])</span> <span class="gp">>>> </span><span class="n">e</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">({</span><span class="s1">'three'</span><span class="p">:</span> <span class="mi">3</span><span class="p">,</span> <span class="s1">'one'</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">'two'</span><span class="p">:</span> <span class="mi">2</span><span class="p">})</span> <span class="gp">>>> </span><span class="n">a</span> <span class="o">==</span> <span class="n">b</span> <span class="o">==</span> <span class="n">c</span> <span class="o">==</span> <span class="n">d</span> <span class="o">==</span> <span class="n">e</span> <span class="go">True</span> </pre></div> </div> <p>Providing keyword arguments as in the first example only works for keys that are valid Python identifiers. Otherwise, any valid keys can be used.</p> <p>These are the operations that dictionaries support (and therefore, custom mapping types should support too):</p> <dl class="describe"> <dt> <code class="descname">len(d)</code></dt> <dd><p>Return the number of items in the dictionary <em>d</em>.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">d[key]</code></dt> <dd><p>Return the item of <em>d</em> with key <em>key</em>. Raises a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> if <em>key</em> is not in the map.</p> <p id="index-47">If a subclass of dict defines a method <a class="reference internal" href="../reference/datamodel.html#object.__missing__" title="object.__missing__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__missing__()</span></code></a> and <em>key</em> is not present, the <code class="docutils literal notranslate"><span class="pre">d[key]</span></code> operation calls that method with the key <em>key</em> as argument. The <code class="docutils literal notranslate"><span class="pre">d[key]</span></code> operation then returns or raises whatever is returned or raised by the <code class="docutils literal notranslate"><span class="pre">__missing__(key)</span></code> call. No other operations or methods invoke <a class="reference internal" href="../reference/datamodel.html#object.__missing__" title="object.__missing__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__missing__()</span></code></a>. If <a class="reference internal" href="../reference/datamodel.html#object.__missing__" title="object.__missing__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__missing__()</span></code></a> is not defined, <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> is raised. <a class="reference internal" href="../reference/datamodel.html#object.__missing__" title="object.__missing__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__missing__()</span></code></a> must be a method; it cannot be an instance variable:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">class</span> <span class="nc">Counter</span><span class="p">(</span><span class="nb">dict</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">__missing__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">):</span> <span class="gp">... </span> <span class="k">return</span> <span class="mi">0</span> <span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">Counter</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">c</span><span class="p">[</span><span class="s1">'red'</span><span class="p">]</span> <span class="go">0</span> <span class="gp">>>> </span><span class="n">c</span><span class="p">[</span><span class="s1">'red'</span><span class="p">]</span> <span class="o">+=</span> <span class="mi">1</span> <span class="gp">>>> </span><span class="n">c</span><span class="p">[</span><span class="s1">'red'</span><span class="p">]</span> <span class="go">1</span> </pre></div> </div> <p>The example above shows part of the implementation of <a class="reference internal" href="collections.html#collections.Counter" title="collections.Counter"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.Counter</span></code></a>. A different <code class="docutils literal notranslate"><span class="pre">__missing__</span></code> method is used by <a class="reference internal" href="collections.html#collections.defaultdict" title="collections.defaultdict"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.defaultdict</span></code></a>.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">d[key] = value</code></dt> <dd><p>Set <code class="docutils literal notranslate"><span class="pre">d[key]</span></code> to <em>value</em>.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">del d[key]</code></dt> <dd><p>Remove <code class="docutils literal notranslate"><span class="pre">d[key]</span></code> from <em>d</em>. Raises a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> if <em>key</em> is not in the map.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">key in d</code></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if <em>d</em> has a key <em>key</em>, else <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">key not in d</code></dt> <dd><p>Equivalent to <code class="docutils literal notranslate"><span class="pre">not</span> <span class="pre">key</span> <span class="pre">in</span> <span class="pre">d</span></code>.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">iter(d)</code></dt> <dd><p>Return an iterator over the keys of the dictionary. This is a shortcut for <code class="docutils literal notranslate"><span class="pre">iter(d.keys())</span></code>.</p> </dd></dl> <dl class="method"> <dt id="dict.clear"> <code class="descname">clear</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.clear" title="Permalink to this definition">¶</a></dt> <dd><p>Remove all items from the dictionary.</p> </dd></dl> <dl class="method"> <dt id="dict.copy"> <code class="descname">copy</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.copy" title="Permalink to this definition">¶</a></dt> <dd><p>Return a shallow copy of the dictionary.</p> </dd></dl> <dl class="classmethod"> <dt id="dict.fromkeys"> <em class="property">classmethod </em><code class="descname">fromkeys</code><span class="sig-paren">(</span><em>seq</em><span class="optional">[</span>, <em>value</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.fromkeys" title="Permalink to this definition">¶</a></dt> <dd><p>Create a new dictionary with keys from <em>seq</em> and values set to <em>value</em>.</p> <p><a class="reference internal" href="#dict.fromkeys" title="dict.fromkeys"><code class="xref py py-meth docutils literal notranslate"><span class="pre">fromkeys()</span></code></a> is a class method that returns a new dictionary. <em>value</em> defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="method"> <dt id="dict.get"> <code class="descname">get</code><span class="sig-paren">(</span><em>key</em><span class="optional">[</span>, <em>default</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.get" title="Permalink to this definition">¶</a></dt> <dd><p>Return the value for <em>key</em> if <em>key</em> is in the dictionary, else <em>default</em>. If <em>default</em> is not given, it defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>, so that this method never raises a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a>.</p> </dd></dl> <dl class="method"> <dt id="dict.items"> <code class="descname">items</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.items" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new view of the dictionary’s items (<code class="docutils literal notranslate"><span class="pre">(key,</span> <span class="pre">value)</span></code> pairs). See the <a class="reference internal" href="#dict-views"><span class="std std-ref">documentation of view objects</span></a>.</p> </dd></dl> <dl class="method"> <dt id="dict.keys"> <code class="descname">keys</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.keys" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new view of the dictionary’s keys. See the <a class="reference internal" href="#dict-views"><span class="std std-ref">documentation of view objects</span></a>.</p> </dd></dl> <dl class="method"> <dt id="dict.pop"> <code class="descname">pop</code><span class="sig-paren">(</span><em>key</em><span class="optional">[</span>, <em>default</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.pop" title="Permalink to this definition">¶</a></dt> <dd><p>If <em>key</em> is in the dictionary, remove it and return its value, else return <em>default</em>. If <em>default</em> is not given and <em>key</em> is not in the dictionary, a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a> is raised.</p> </dd></dl> <dl class="method"> <dt id="dict.popitem"> <code class="descname">popitem</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.popitem" title="Permalink to this definition">¶</a></dt> <dd><p>Remove and return an arbitrary <code class="docutils literal notranslate"><span class="pre">(key,</span> <span class="pre">value)</span></code> pair from the dictionary.</p> <p><a class="reference internal" href="#dict.popitem" title="dict.popitem"><code class="xref py py-meth docutils literal notranslate"><span class="pre">popitem()</span></code></a> is useful to destructively iterate over a dictionary, as often used in set algorithms. If the dictionary is empty, calling <a class="reference internal" href="#dict.popitem" title="dict.popitem"><code class="xref py py-meth docutils literal notranslate"><span class="pre">popitem()</span></code></a> raises a <a class="reference internal" href="exceptions.html#KeyError" title="KeyError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyError</span></code></a>.</p> </dd></dl> <dl class="method"> <dt id="dict.setdefault"> <code class="descname">setdefault</code><span class="sig-paren">(</span><em>key</em><span class="optional">[</span>, <em>default</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.setdefault" title="Permalink to this definition">¶</a></dt> <dd><p>If <em>key</em> is in the dictionary, return its value. If not, insert <em>key</em> with a value of <em>default</em> and return <em>default</em>. <em>default</em> defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </dd></dl> <dl class="method"> <dt id="dict.update"> <code class="descname">update</code><span class="sig-paren">(</span><span class="optional">[</span><em>other</em><span class="optional">]</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.update" title="Permalink to this definition">¶</a></dt> <dd><p>Update the dictionary with the key/value pairs from <em>other</em>, overwriting existing keys. Return <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> <p><a class="reference internal" href="#dict.update" title="dict.update"><code class="xref py py-meth docutils literal notranslate"><span class="pre">update()</span></code></a> accepts either another dictionary object or an iterable of key/value pairs (as tuples or other iterables of length two). If keyword arguments are specified, the dictionary is then updated with those key/value pairs: <code class="docutils literal notranslate"><span class="pre">d.update(red=1,</span> <span class="pre">blue=2)</span></code>.</p> </dd></dl> <dl class="method"> <dt id="dict.values"> <code class="descname">values</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#dict.values" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new view of the dictionary’s values. See the <a class="reference internal" href="#dict-views"><span class="std std-ref">documentation of view objects</span></a>.</p> </dd></dl> <p>Dictionaries compare equal if and only if they have the same <code class="docutils literal notranslate"><span class="pre">(key,</span> <span class="pre">value)</span></code> pairs. Order comparisons (‘<’, ‘<=’, ‘>=’, ‘>’) raise <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> </dd></dl> <div class="admonition seealso"> <p class="first admonition-title">See also</p> <p class="last"><a class="reference internal" href="types.html#types.MappingProxyType" title="types.MappingProxyType"><code class="xref py py-class docutils literal notranslate"><span class="pre">types.MappingProxyType</span></code></a> can be used to create a read-only view of a <a class="reference internal" href="#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a>.</p> </div> <div class="section" id="dictionary-view-objects"> <span id="dict-views"></span><h3>4.10.1. Dictionary view objects<a class="headerlink" href="#dictionary-view-objects" title="Permalink to this headline">¶</a></h3> <p>The objects returned by <a class="reference internal" href="#dict.keys" title="dict.keys"><code class="xref py py-meth docutils literal notranslate"><span class="pre">dict.keys()</span></code></a>, <a class="reference internal" href="#dict.values" title="dict.values"><code class="xref py py-meth docutils literal notranslate"><span class="pre">dict.values()</span></code></a> and <a class="reference internal" href="#dict.items" title="dict.items"><code class="xref py py-meth docutils literal notranslate"><span class="pre">dict.items()</span></code></a> are <em>view objects</em>. They provide a dynamic view on the dictionary’s entries, which means that when the dictionary changes, the view reflects these changes.</p> <p>Dictionary views can be iterated over to yield their respective data, and support membership tests:</p> <dl class="describe"> <dt> <code class="descname">len(dictview)</code></dt> <dd><p>Return the number of entries in the dictionary.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">iter(dictview)</code></dt> <dd><p>Return an iterator over the keys, values or items (represented as tuples of <code class="docutils literal notranslate"><span class="pre">(key,</span> <span class="pre">value)</span></code>) in the dictionary.</p> <p>Keys and values are iterated over in an arbitrary order which is non-random, varies across Python implementations, and depends on the dictionary’s history of insertions and deletions. If keys, values and items views are iterated over with no intervening modifications to the dictionary, the order of items will directly correspond. This allows the creation of <code class="docutils literal notranslate"><span class="pre">(value,</span> <span class="pre">key)</span></code> pairs using <a class="reference internal" href="functions.html#zip" title="zip"><code class="xref py py-func docutils literal notranslate"><span class="pre">zip()</span></code></a>: <code class="docutils literal notranslate"><span class="pre">pairs</span> <span class="pre">=</span> <span class="pre">zip(d.values(),</span> <span class="pre">d.keys())</span></code>. Another way to create the same list is <code class="docutils literal notranslate"><span class="pre">pairs</span> <span class="pre">=</span> <span class="pre">[(v,</span> <span class="pre">k)</span> <span class="pre">for</span> <span class="pre">(k,</span> <span class="pre">v)</span> <span class="pre">in</span> <span class="pre">d.items()]</span></code>.</p> <p>Iterating views while adding or deleting entries in the dictionary may raise a <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeError</span></code></a> or fail to iterate over all entries.</p> </dd></dl> <dl class="describe"> <dt> <code class="descname">x in dictview</code></dt> <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if <em>x</em> is in the underlying dictionary’s keys, values or items (in the latter case, <em>x</em> should be a <code class="docutils literal notranslate"><span class="pre">(key,</span> <span class="pre">value)</span></code> tuple).</p> </dd></dl> <p>Keys views are set-like since their entries are unique and hashable. If all values are hashable, so that <code class="docutils literal notranslate"><span class="pre">(key,</span> <span class="pre">value)</span></code> pairs are unique and hashable, then the items view is also set-like. (Values views are not treated as set-like since the entries are generally not unique.) For set-like views, all of the operations defined for the abstract base class <a class="reference internal" href="collections.abc.html#collections.abc.Set" title="collections.abc.Set"><code class="xref py py-class docutils literal notranslate"><span class="pre">collections.abc.Set</span></code></a> are available (for example, <code class="docutils literal notranslate"><span class="pre">==</span></code>, <code class="docutils literal notranslate"><span class="pre"><</span></code>, or <code class="docutils literal notranslate"><span class="pre">^</span></code>).</p> <p>An example of dictionary view usage:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">dishes</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'eggs'</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="s1">'sausage'</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">'bacon'</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span> <span class="s1">'spam'</span><span class="p">:</span> <span class="mi">500</span><span class="p">}</span> <span class="gp">>>> </span><span class="n">keys</span> <span class="o">=</span> <span class="n">dishes</span><span class="o">.</span><span class="n">keys</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">values</span> <span class="o">=</span> <span class="n">dishes</span><span class="o">.</span><span class="n">values</span><span class="p">()</span> <span class="gp">>>> </span><span class="c1"># iteration</span> <span class="gp">>>> </span><span class="n">n</span> <span class="o">=</span> <span class="mi">0</span> <span class="gp">>>> </span><span class="k">for</span> <span class="n">val</span> <span class="ow">in</span> <span class="n">values</span><span class="p">:</span> <span class="gp">... </span> <span class="n">n</span> <span class="o">+=</span> <span class="n">val</span> <span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="n">n</span><span class="p">)</span> <span class="go">504</span> <span class="gp">>>> </span><span class="c1"># keys and values are iterated over in the same order</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span> <span class="go">['eggs', 'bacon', 'sausage', 'spam']</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">values</span><span class="p">)</span> <span class="go">[2, 1, 1, 500]</span> <span class="gp">>>> </span><span class="c1"># view objects are dynamic and reflect dict changes</span> <span class="gp">>>> </span><span class="k">del</span> <span class="n">dishes</span><span class="p">[</span><span class="s1">'eggs'</span><span class="p">]</span> <span class="gp">>>> </span><span class="k">del</span> <span class="n">dishes</span><span class="p">[</span><span class="s1">'sausage'</span><span class="p">]</span> <span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">keys</span><span class="p">)</span> <span class="go">['spam', 'bacon']</span> <span class="gp">>>> </span><span class="c1"># set operations</span> <span class="gp">>>> </span><span class="n">keys</span> <span class="o">&</span> <span class="p">{</span><span class="s1">'eggs'</span><span class="p">,</span> <span class="s1">'bacon'</span><span class="p">,</span> <span class="s1">'salad'</span><span class="p">}</span> <span class="go">{'bacon'}</span> <span class="gp">>>> </span><span class="n">keys</span> <span class="o">^</span> <span class="p">{</span><span class="s1">'sausage'</span><span class="p">,</span> <span class="s1">'juice'</span><span class="p">}</span> <span class="go">{'juice', 'sausage', 'bacon', 'spam'}</span> </pre></div> </div> </div> </div> <div class="section" id="context-manager-types"> <span id="typecontextmanager"></span><h2>4.11. Context Manager Types<a class="headerlink" href="#context-manager-types" title="Permalink to this headline">¶</a></h2> <p id="index-48">Python’s <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement supports the concept of a runtime context defined by a context manager. This is implemented using a pair of methods that allow user-defined classes to define a runtime context that is entered before the statement body is executed and exited when the statement ends:</p> <dl class="method"> <dt id="contextmanager.__enter__"> <code class="descclassname">contextmanager.</code><code class="descname">__enter__</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#contextmanager.__enter__" title="Permalink to this definition">¶</a></dt> <dd><p>Enter the runtime context and return either this object or another object related to the runtime context. The value returned by this method is bound to the identifier in the <a class="reference internal" href="../reference/compound_stmts.html#as"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">as</span></code></a> clause of <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statements using this context manager.</p> <p>An example of a context manager that returns itself is a <a class="reference internal" href="../glossary.html#term-file-object"><span class="xref std std-term">file object</span></a>. File objects return themselves from __enter__() to allow <a class="reference internal" href="functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a> to be used as the context expression in a <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement.</p> <p>An example of a context manager that returns a related object is the one returned by <a class="reference internal" href="decimal.html#decimal.localcontext" title="decimal.localcontext"><code class="xref py py-func docutils literal notranslate"><span class="pre">decimal.localcontext()</span></code></a>. These managers set the active decimal context to a copy of the original decimal context and then return the copy. This allows changes to be made to the current decimal context in the body of the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement without affecting code outside the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement.</p> </dd></dl> <dl class="method"> <dt id="contextmanager.__exit__"> <code class="descclassname">contextmanager.</code><code class="descname">__exit__</code><span class="sig-paren">(</span><em>exc_type</em>, <em>exc_val</em>, <em>exc_tb</em><span class="sig-paren">)</span><a class="headerlink" href="#contextmanager.__exit__" title="Permalink to this definition">¶</a></dt> <dd><p>Exit the runtime context and return a Boolean flag indicating if any exception that occurred should be suppressed. If an exception occurred while executing the body of the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement, the arguments contain the exception type, value and traceback information. Otherwise, all three arguments are <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> <p>Returning a true value from this method will cause the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement to suppress the exception and continue execution with the statement immediately following the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement. Otherwise the exception continues propagating after this method has finished executing. Exceptions that occur during execution of this method will replace any exception that occurred in the body of the <a class="reference internal" href="../reference/compound_stmts.html#with"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">with</span></code></a> statement.</p> <p>The exception passed in should never be reraised explicitly - instead, this method should return a false value to indicate that the method completed successfully and does not want to suppress the raised exception. This allows context management code to easily detect whether or not an <a class="reference internal" href="#contextmanager.__exit__" title="contextmanager.__exit__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__exit__()</span></code></a> method has actually failed.</p> </dd></dl> <p>Python defines several context managers to support easy thread synchronisation, prompt closure of files or other objects, and simpler manipulation of the active decimal arithmetic context. The specific types are not treated specially beyond their implementation of the context management protocol. See the <a class="reference internal" href="contextlib.html#module-contextlib" title="contextlib: Utilities for with-statement contexts."><code class="xref py py-mod docutils literal notranslate"><span class="pre">contextlib</span></code></a> module for some examples.</p> <p>Python’s <a class="reference internal" href="../glossary.html#term-generator"><span class="xref std std-term">generator</span></a>s and the <a class="reference internal" href="contextlib.html#contextlib.contextmanager" title="contextlib.contextmanager"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextlib.contextmanager</span></code></a> decorator provide a convenient way to implement these protocols. If a generator function is decorated with the <a class="reference internal" href="contextlib.html#contextlib.contextmanager" title="contextlib.contextmanager"><code class="xref py py-class docutils literal notranslate"><span class="pre">contextlib.contextmanager</span></code></a> decorator, it will return a context manager implementing the necessary <a class="reference internal" href="../reference/datamodel.html#object.__enter__" title="object.__enter__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__enter__()</span></code></a> and <a class="reference internal" href="../reference/datamodel.html#object.__exit__" title="object.__exit__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__exit__()</span></code></a> methods, rather than the iterator produced by an undecorated generator function.</p> <p>Note that there is no specific slot for any of these methods in the type structure for Python objects in the Python/C API. Extension types wanting to define these methods must provide them as a normal Python accessible method. Compared to the overhead of setting up the runtime context, the overhead of a single class dictionary lookup is negligible.</p> </div> <div class="section" id="other-built-in-types"> <span id="typesother"></span><h2>4.12. Other Built-in Types<a class="headerlink" href="#other-built-in-types" title="Permalink to this headline">¶</a></h2> <p>The interpreter supports several other kinds of objects. Most of these support only one or two operations.</p> <div class="section" id="modules"> <span id="typesmodules"></span><h3>4.12.1. Modules<a class="headerlink" href="#modules" title="Permalink to this headline">¶</a></h3> <p>The only special operation on a module is attribute access: <code class="docutils literal notranslate"><span class="pre">m.name</span></code>, where <em>m</em> is a module and <em>name</em> accesses a name defined in <em>m</em>’s symbol table. Module attributes can be assigned to. (Note that the <a class="reference internal" href="../reference/simple_stmts.html#import"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">import</span></code></a> statement is not, strictly speaking, an operation on a module object; <code class="docutils literal notranslate"><span class="pre">import</span> <span class="pre">foo</span></code> does not require a module object named <em>foo</em> to exist, rather it requires an (external) <em>definition</em> for a module named <em>foo</em> somewhere.)</p> <p>A special attribute of every module is <a class="reference internal" href="#object.__dict__" title="object.__dict__"><code class="xref py py-attr docutils literal notranslate"><span class="pre">__dict__</span></code></a>. This is the dictionary containing the module’s symbol table. Modifying this dictionary will actually change the module’s symbol table, but direct assignment to the <a class="reference internal" href="#object.__dict__" title="object.__dict__"><code class="xref py py-attr docutils literal notranslate"><span class="pre">__dict__</span></code></a> attribute is not possible (you can write <code class="docutils literal notranslate"><span class="pre">m.__dict__['a']</span> <span class="pre">=</span> <span class="pre">1</span></code>, which defines <code class="docutils literal notranslate"><span class="pre">m.a</span></code> to be <code class="docutils literal notranslate"><span class="pre">1</span></code>, but you can’t write <code class="docutils literal notranslate"><span class="pre">m.__dict__</span> <span class="pre">=</span> <span class="pre">{}</span></code>). Modifying <a class="reference internal" href="#object.__dict__" title="object.__dict__"><code class="xref py py-attr docutils literal notranslate"><span class="pre">__dict__</span></code></a> directly is not recommended.</p> <p>Modules built into the interpreter are written like this: <code class="docutils literal notranslate"><span class="pre"><module</span> <span class="pre">'sys'</span> <span class="pre">(built-in)></span></code>. If loaded from a file, they are written as <code class="docutils literal notranslate"><span class="pre"><module</span> <span class="pre">'os'</span> <span class="pre">from</span> <span class="pre">'/usr/local/lib/pythonX.Y/os.pyc'></span></code>.</p> </div> <div class="section" id="classes-and-class-instances"> <span id="typesobjects"></span><h3>4.12.2. Classes and Class Instances<a class="headerlink" href="#classes-and-class-instances" title="Permalink to this headline">¶</a></h3> <p>See <a class="reference internal" href="../reference/datamodel.html#objects"><span class="std std-ref">Objects, values and types</span></a> and <a class="reference internal" href="../reference/compound_stmts.html#class"><span class="std std-ref">Class definitions</span></a> for these.</p> </div> <div class="section" id="functions"> <span id="typesfunctions"></span><h3>4.12.3. Functions<a class="headerlink" href="#functions" title="Permalink to this headline">¶</a></h3> <p>Function objects are created by function definitions. The only operation on a function object is to call it: <code class="docutils literal notranslate"><span class="pre">func(argument-list)</span></code>.</p> <p>There are really two flavors of function objects: built-in functions and user-defined functions. Both support the same operation (to call the function), but the implementation is different, hence the different object types.</p> <p>See <a class="reference internal" href="../reference/compound_stmts.html#function"><span class="std std-ref">Function definitions</span></a> for more information.</p> </div> <div class="section" id="methods"> <span id="typesmethods"></span><h3>4.12.4. Methods<a class="headerlink" href="#methods" title="Permalink to this headline">¶</a></h3> <p id="index-49">Methods are functions that are called using the attribute notation. There are two flavors: built-in methods (such as <code class="xref py py-meth docutils literal notranslate"><span class="pre">append()</span></code> on lists) and class instance methods. Built-in methods are described with the types that support them.</p> <p>If you access a method (a function defined in a class namespace) through an instance, you get a special object: a <em class="dfn">bound method</em> (also called <em class="dfn">instance method</em>) object. When called, it will add the <code class="docutils literal notranslate"><span class="pre">self</span></code> argument to the argument list. Bound methods have two special read-only attributes: <code class="docutils literal notranslate"><span class="pre">m.__self__</span></code> is the object on which the method operates, and <code class="docutils literal notranslate"><span class="pre">m.__func__</span></code> is the function implementing the method. Calling <code class="docutils literal notranslate"><span class="pre">m(arg-1,</span> <span class="pre">arg-2,</span> <span class="pre">...,</span> <span class="pre">arg-n)</span></code> is completely equivalent to calling <code class="docutils literal notranslate"><span class="pre">m.__func__(m.__self__,</span> <span class="pre">arg-1,</span> <span class="pre">arg-2,</span> <span class="pre">...,</span> <span class="pre">arg-n)</span></code>.</p> <p>Like function objects, bound method objects support getting arbitrary attributes. However, since method attributes are actually stored on the underlying function object (<code class="docutils literal notranslate"><span class="pre">meth.__func__</span></code>), setting method attributes on bound methods is disallowed. Attempting to set an attribute on a method results in an <a class="reference internal" href="exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">AttributeError</span></code></a> being raised. In order to set a method attribute, you need to explicitly set it on the underlying function object:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">class</span> <span class="nc">C</span><span class="p">:</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">method</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <span class="gp">... </span> <span class="k">pass</span> <span class="gp">...</span> <span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">C</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">method</span><span class="o">.</span><span class="n">whoami</span> <span class="o">=</span> <span class="s1">'my name is method'</span> <span class="c1"># can't set on the method</span> <span class="gt">Traceback (most recent call last):</span> File <span class="nb">"<stdin>"</span>, line <span class="m">1</span>, in <span class="n"><module></span> <span class="gr">AttributeError</span>: <span class="n">'method' object has no attribute 'whoami'</span> <span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">method</span><span class="o">.</span><span class="vm">__func__</span><span class="o">.</span><span class="n">whoami</span> <span class="o">=</span> <span class="s1">'my name is method'</span> <span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">method</span><span class="o">.</span><span class="n">whoami</span> <span class="go">'my name is method'</span> </pre></div> </div> <p>See <a class="reference internal" href="../reference/datamodel.html#types"><span class="std std-ref">The standard type hierarchy</span></a> for more information.</p> </div> <div class="section" id="code-objects"> <span id="bltin-code-objects"></span><span id="index-50"></span><h3>4.12.5. Code Objects<a class="headerlink" href="#code-objects" title="Permalink to this headline">¶</a></h3> <p id="index-51">Code objects are used by the implementation to represent “pseudo-compiled” executable Python code such as a function body. They differ from function objects because they don’t contain a reference to their global execution environment. Code objects are returned by the built-in <a class="reference internal" href="functions.html#compile" title="compile"><code class="xref py py-func docutils literal notranslate"><span class="pre">compile()</span></code></a> function and can be extracted from function objects through their <code class="xref py py-attr docutils literal notranslate"><span class="pre">__code__</span></code> attribute. See also the <a class="reference internal" href="code.html#module-code" title="code: Facilities to implement read-eval-print loops."><code class="xref py py-mod docutils literal notranslate"><span class="pre">code</span></code></a> module.</p> <p id="index-52">A code object can be executed or evaluated by passing it (instead of a source string) to the <a class="reference internal" href="functions.html#exec" title="exec"><code class="xref py py-func docutils literal notranslate"><span class="pre">exec()</span></code></a> or <a class="reference internal" href="functions.html#eval" title="eval"><code class="xref py py-func docutils literal notranslate"><span class="pre">eval()</span></code></a> built-in functions.</p> <p>See <a class="reference internal" href="../reference/datamodel.html#types"><span class="std std-ref">The standard type hierarchy</span></a> for more information.</p> </div> <div class="section" id="type-objects"> <span id="bltin-type-objects"></span><h3>4.12.6. Type Objects<a class="headerlink" href="#type-objects" title="Permalink to this headline">¶</a></h3> <p id="index-53">Type objects represent the various object types. An object’s type is accessed by the built-in function <a class="reference internal" href="functions.html#type" title="type"><code class="xref py py-func docutils literal notranslate"><span class="pre">type()</span></code></a>. There are no special operations on types. The standard module <a class="reference internal" href="types.html#module-types" title="types: Names for built-in types."><code class="xref py py-mod docutils literal notranslate"><span class="pre">types</span></code></a> defines names for all standard built-in types.</p> <p>Types are written like this: <code class="docutils literal notranslate"><span class="pre"><class</span> <span class="pre">'int'></span></code>.</p> </div> <div class="section" id="the-null-object"> <span id="bltin-null-object"></span><h3>4.12.7. The Null Object<a class="headerlink" href="#the-null-object" title="Permalink to this headline">¶</a></h3> <p>This object is returned by functions that don’t explicitly return a value. It supports no special operations. There is exactly one null object, named <code class="docutils literal notranslate"><span class="pre">None</span></code> (a built-in name). <code class="docutils literal notranslate"><span class="pre">type(None)()</span></code> produces the same singleton.</p> <p>It is written as <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p> </div> <div class="section" id="the-ellipsis-object"> <span id="bltin-ellipsis-object"></span><h3>4.12.8. The Ellipsis Object<a class="headerlink" href="#the-ellipsis-object" title="Permalink to this headline">¶</a></h3> <p>This object is commonly used by slicing (see <a class="reference internal" href="../reference/expressions.html#slicings"><span class="std std-ref">Slicings</span></a>). It supports no special operations. There is exactly one ellipsis object, named <a class="reference internal" href="constants.html#Ellipsis" title="Ellipsis"><code class="xref py py-const docutils literal notranslate"><span class="pre">Ellipsis</span></code></a> (a built-in name). <code class="docutils literal notranslate"><span class="pre">type(Ellipsis)()</span></code> produces the <a class="reference internal" href="constants.html#Ellipsis" title="Ellipsis"><code class="xref py py-const docutils literal notranslate"><span class="pre">Ellipsis</span></code></a> singleton.</p> <p>It is written as <code class="docutils literal notranslate"><span class="pre">Ellipsis</span></code> or <code class="docutils literal notranslate"><span class="pre">...</span></code>.</p> </div> <div class="section" id="the-notimplemented-object"> <span id="bltin-notimplemented-object"></span><h3>4.12.9. The NotImplemented Object<a class="headerlink" href="#the-notimplemented-object" title="Permalink to this headline">¶</a></h3> <p>This object is returned from comparisons and binary operations when they are asked to operate on types they don’t support. See <a class="reference internal" href="../reference/expressions.html#comparisons"><span class="std std-ref">Comparisons</span></a> for more information. There is exactly one <code class="docutils literal notranslate"><span class="pre">NotImplemented</span></code> object. <code class="docutils literal notranslate"><span class="pre">type(NotImplemented)()</span></code> produces the singleton instance.</p> <p>It is written as <code class="docutils literal notranslate"><span class="pre">NotImplemented</span></code>.</p> </div> <div class="section" id="boolean-values"> <span id="bltin-boolean-values"></span><h3>4.12.10. Boolean Values<a class="headerlink" href="#boolean-values" title="Permalink to this headline">¶</a></h3> <p>Boolean values are the two constant objects <code class="docutils literal notranslate"><span class="pre">False</span></code> and <code class="docutils literal notranslate"><span class="pre">True</span></code>. They are used to represent truth values (although other values can also be considered false or true). In numeric contexts (for example when used as the argument to an arithmetic operator), they behave like the integers 0 and 1, respectively. The built-in function <a class="reference internal" href="functions.html#bool" title="bool"><code class="xref py py-func docutils literal notranslate"><span class="pre">bool()</span></code></a> can be used to convert any value to a Boolean, if the value can be interpreted as a truth value (see section <a class="reference internal" href="#truth"><span class="std std-ref">Truth Value Testing</span></a> above).</p> <p id="index-54">They are written as <code class="docutils literal notranslate"><span class="pre">False</span></code> and <code class="docutils literal notranslate"><span class="pre">True</span></code>, respectively.</p> </div> <div class="section" id="internal-objects"> <span id="typesinternal"></span><h3>4.12.11. Internal Objects<a class="headerlink" href="#internal-objects" title="Permalink to this headline">¶</a></h3> <p>See <a class="reference internal" href="../reference/datamodel.html#types"><span class="std std-ref">The standard type hierarchy</span></a> for this information. It describes stack frame objects, traceback objects, and slice objects.</p> </div> </div> <div class="section" id="special-attributes"> <span id="specialattrs"></span><h2>4.13. Special Attributes<a class="headerlink" href="#special-attributes" title="Permalink to this headline">¶</a></h2> <p>The implementation adds a few special read-only attributes to several object types, where they are relevant. Some of these are not reported by the <a class="reference internal" href="functions.html#dir" title="dir"><code class="xref py py-func docutils literal notranslate"><span class="pre">dir()</span></code></a> built-in function.</p> <dl class="attribute"> <dt id="object.__dict__"> <code class="descclassname">object.</code><code class="descname">__dict__</code><a class="headerlink" href="#object.__dict__" title="Permalink to this definition">¶</a></dt> <dd><p>A dictionary or other mapping object used to store an object’s (writable) attributes.</p> </dd></dl> <dl class="attribute"> <dt id="instance.__class__"> <code class="descclassname">instance.</code><code class="descname">__class__</code><a class="headerlink" href="#instance.__class__" title="Permalink to this definition">¶</a></dt> <dd><p>The class to which a class instance belongs.</p> </dd></dl> <dl class="attribute"> <dt id="class.__bases__"> <code class="descclassname">class.</code><code class="descname">__bases__</code><a class="headerlink" href="#class.__bases__" title="Permalink to this definition">¶</a></dt> <dd><p>The tuple of base classes of a class object.</p> </dd></dl> <dl class="attribute"> <dt id="definition.__name__"> <code class="descclassname">definition.</code><code class="descname">__name__</code><a class="headerlink" href="#definition.__name__" title="Permalink to this definition">¶</a></dt> <dd><p>The name of the class, function, method, descriptor, or generator instance.</p> </dd></dl> <dl class="attribute"> <dt id="definition.__qualname__"> <code class="descclassname">definition.</code><code class="descname">__qualname__</code><a class="headerlink" href="#definition.__qualname__" title="Permalink to this definition">¶</a></dt> <dd><p>The <a class="reference internal" href="../glossary.html#term-qualified-name"><span class="xref std std-term">qualified name</span></a> of the class, function, method, descriptor, or generator instance.</p> <div class="versionadded"> <p><span class="versionmodified">New in version 3.3.</span></p> </div> </dd></dl> <dl class="attribute"> <dt id="class.__mro__"> <code class="descclassname">class.</code><code class="descname">__mro__</code><a class="headerlink" href="#class.__mro__" title="Permalink to this definition">¶</a></dt> <dd><p>This attribute is a tuple of classes that are considered when looking for base classes during method resolution.</p> </dd></dl> <dl class="method"> <dt id="class.mro"> <code class="descclassname">class.</code><code class="descname">mro</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#class.mro" title="Permalink to this definition">¶</a></dt> <dd><p>This method can be overridden by a metaclass to customize the method resolution order for its instances. It is called at class instantiation, and its result is stored in <a class="reference internal" href="#class.__mro__" title="class.__mro__"><code class="xref py py-attr docutils literal notranslate"><span class="pre">__mro__</span></code></a>.</p> </dd></dl> <dl class="method"> <dt id="class.__subclasses__"> <code class="descclassname">class.</code><code class="descname">__subclasses__</code><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#class.__subclasses__" title="Permalink to this definition">¶</a></dt> <dd><p>Each class keeps a list of weak references to its immediate subclasses. This method returns a list of all those references still alive. Example:</p> <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">int</span><span class="o">.</span><span class="n">__subclasses__</span><span class="p">()</span> <span class="go">[<class 'bool'>]</span> </pre></div> </div> </dd></dl> <p class="rubric">Footnotes</p> <table class="docutils footnote" frame="void" id="id12" rules="none"> <colgroup><col class="label" /><col /></colgroup> <tbody valign="top"> <tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>Additional information on these special methods may be found in the Python Reference Manual (<a class="reference internal" href="../reference/datamodel.html#customization"><span class="std std-ref">Basic customization</span></a>).</td></tr> </tbody> </table> <table class="docutils footnote" frame="void" id="id13" rules="none"> <colgroup><col class="label" /><col /></colgroup> <tbody valign="top"> <tr><td class="label"><a class="fn-backref" href="#id2">[2]</a></td><td>As a consequence, the list <code class="docutils literal notranslate"><span class="pre">[1,</span> <span class="pre">2]</span></code> is considered equal to <code class="docutils literal notranslate"><span class="pre">[1.0,</span> <span class="pre">2.0]</span></code>, and similarly for tuples.</td></tr> </tbody> </table> <table class="docutils footnote" frame="void" id="id14" rules="none"> <colgroup><col class="label" /><col /></colgroup> <tbody valign="top"> <tr><td class="label"><a class="fn-backref" href="#id4">[3]</a></td><td>They must have since the parser can’t tell the type of the operands.</td></tr> </tbody> </table> <table class="docutils footnote" frame="void" id="id15" rules="none"> <colgroup><col class="label" /><col /></colgroup> <tbody valign="top"> <tr><td class="label">[4]</td><td><em>(<a class="fn-backref" href="#id6">1</a>, <a class="fn-backref" href="#id7">2</a>, <a class="fn-backref" href="#id8">3</a>, <a class="fn-backref" href="#id9">4</a>)</em> Cased characters are those with general category property being one of “Lu” (Letter, uppercase), “Ll” (Letter, lowercase), or “Lt” (Letter, titlecase).</td></tr> </tbody> </table> <table class="docutils footnote" frame="void" id="id16" rules="none"> <colgroup><col class="label" /><col /></colgroup> <tbody valign="top"> <tr><td class="label">[5]</td><td><em>(<a class="fn-backref" href="#id10">1</a>, <a class="fn-backref" href="#id11">2</a>)</em> To format only a tuple you should therefore provide a singleton tuple whose only element is the tuple to be formatted.</td></tr> </tbody> </table> </div> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h3><a href="../contents.html">Table Of Contents</a></h3> <ul> <li><a class="reference internal" href="#">4. Built-in Types</a><ul> <li><a class="reference internal" href="#truth-value-testing">4.1. Truth Value Testing</a></li> <li><a class="reference internal" href="#boolean-operations-and-or-not">4.2. Boolean Operations — <code class="docutils literal notranslate"><span class="pre">and</span></code>, <code class="docutils literal notranslate"><span class="pre">or</span></code>, <code class="docutils literal notranslate"><span class="pre">not</span></code></a></li> <li><a class="reference internal" href="#comparisons">4.3. Comparisons</a></li> <li><a class="reference internal" href="#numeric-types-int-float-complex">4.4. Numeric Types — <code class="docutils literal notranslate"><span class="pre">int</span></code>, <code class="docutils literal notranslate"><span class="pre">float</span></code>, <code class="docutils literal notranslate"><span class="pre">complex</span></code></a><ul> <li><a class="reference internal" href="#bitwise-operations-on-integer-types">4.4.1. Bitwise Operations on Integer Types</a></li> <li><a class="reference internal" href="#additional-methods-on-integer-types">4.4.2. Additional Methods on Integer Types</a></li> <li><a class="reference internal" href="#additional-methods-on-float">4.4.3. Additional Methods on Float</a></li> <li><a class="reference internal" href="#hashing-of-numeric-types">4.4.4. Hashing of numeric types</a></li> </ul> </li> <li><a class="reference internal" href="#iterator-types">4.5. Iterator Types</a><ul> <li><a class="reference internal" href="#generator-types">4.5.1. Generator Types</a></li> </ul> </li> <li><a class="reference internal" href="#sequence-types-list-tuple-range">4.6. Sequence Types — <code class="docutils literal notranslate"><span class="pre">list</span></code>, <code class="docutils literal notranslate"><span class="pre">tuple</span></code>, <code class="docutils literal notranslate"><span class="pre">range</span></code></a><ul> <li><a class="reference internal" href="#common-sequence-operations">4.6.1. Common Sequence Operations</a></li> <li><a class="reference internal" href="#immutable-sequence-types">4.6.2. Immutable Sequence Types</a></li> <li><a class="reference internal" href="#mutable-sequence-types">4.6.3. Mutable Sequence Types</a></li> <li><a class="reference internal" href="#lists">4.6.4. Lists</a></li> <li><a class="reference internal" href="#tuples">4.6.5. Tuples</a></li> <li><a class="reference internal" href="#ranges">4.6.6. Ranges</a></li> </ul> </li> <li><a class="reference internal" href="#text-sequence-type-str">4.7. Text Sequence Type — <code class="docutils literal notranslate"><span class="pre">str</span></code></a><ul> <li><a class="reference internal" href="#string-methods">4.7.1. String Methods</a></li> <li><a class="reference internal" href="#printf-style-string-formatting">4.7.2. <code class="docutils literal notranslate"><span class="pre">printf</span></code>-style String Formatting</a></li> </ul> </li> <li><a class="reference internal" href="#binary-sequence-types-bytes-bytearray-memoryview">4.8. Binary Sequence Types — <code class="docutils literal notranslate"><span class="pre">bytes</span></code>, <code class="docutils literal notranslate"><span class="pre">bytearray</span></code>, <code class="docutils literal notranslate"><span class="pre">memoryview</span></code></a><ul> <li><a class="reference internal" href="#bytes-objects">4.8.1. Bytes Objects</a></li> <li><a class="reference internal" href="#bytearray-objects">4.8.2. Bytearray Objects</a></li> <li><a class="reference internal" href="#bytes-and-bytearray-operations">4.8.3. Bytes and Bytearray Operations</a></li> <li><a class="reference internal" href="#printf-style-bytes-formatting">4.8.4. <code class="docutils literal notranslate"><span class="pre">printf</span></code>-style Bytes Formatting</a></li> <li><a class="reference internal" href="#memory-views">4.8.5. Memory Views</a></li> </ul> </li> <li><a class="reference internal" href="#set-types-set-frozenset">4.9. Set Types — <code class="docutils literal notranslate"><span class="pre">set</span></code>, <code class="docutils literal notranslate"><span class="pre">frozenset</span></code></a></li> <li><a class="reference internal" href="#mapping-types-dict">4.10. Mapping Types — <code class="docutils literal notranslate"><span class="pre">dict</span></code></a><ul> <li><a class="reference internal" href="#dictionary-view-objects">4.10.1. Dictionary view objects</a></li> </ul> </li> <li><a class="reference internal" href="#context-manager-types">4.11. Context Manager Types</a></li> <li><a class="reference internal" href="#other-built-in-types">4.12. Other Built-in Types</a><ul> <li><a class="reference internal" href="#modules">4.12.1. Modules</a></li> <li><a class="reference internal" href="#classes-and-class-instances">4.12.2. Classes and Class Instances</a></li> <li><a class="reference internal" href="#functions">4.12.3. Functions</a></li> <li><a class="reference internal" href="#methods">4.12.4. Methods</a></li> <li><a class="reference internal" href="#code-objects">4.12.5. Code Objects</a></li> <li><a class="reference internal" href="#type-objects">4.12.6. Type Objects</a></li> <li><a class="reference internal" href="#the-null-object">4.12.7. The Null Object</a></li> <li><a class="reference internal" href="#the-ellipsis-object">4.12.8. The Ellipsis Object</a></li> <li><a class="reference internal" href="#the-notimplemented-object">4.12.9. The NotImplemented Object</a></li> <li><a class="reference internal" href="#boolean-values">4.12.10. Boolean Values</a></li> <li><a class="reference internal" href="#internal-objects">4.12.11. Internal Objects</a></li> </ul> </li> <li><a class="reference internal" href="#special-attributes">4.13. Special Attributes</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="constants.html" title="previous chapter">3. Built-in Constants</a></p> <h4>Next topic</h4> <p class="topless"><a href="exceptions.html" title="next chapter">5. 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