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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Bytes Objects — 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="Byte Array Objects" href="bytearray.html" /> <link rel="prev" title="Complex Number Objects" href="complex.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <link rel="canonical" href="https://docs.python.org/3/c-api/bytes.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="bytearray.html" title="Byte Array Objects" accesskey="N">next</a> |</li> <li class="right" > <a href="complex.html" title="Complex Number Objects" 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" >Python/C API Reference Manual</a> »</li> <li class="nav-item nav-item-2"><a href="concrete.html" accesskey="U">Concrete Objects Layer</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="bytes-objects"> <span id="bytesobjects"></span><h1>Bytes Objects<a class="headerlink" href="#bytes-objects" title="Permalink to this headline">¶</a></h1> <p>These functions raise <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> when expecting a bytes parameter and are called with a non-bytes parameter.</p> <span class="target" id="index-0"></span><dl class="type"> <dt id="c.PyBytesObject"> <code class="descname">PyBytesObject</code><a class="headerlink" href="#c.PyBytesObject" title="Permalink to this definition">¶</a></dt> <dd><p>This subtype of <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyObject</span></code></a> represents a Python bytes object.</p> </dd></dl> <dl class="var"> <dt id="c.PyBytes_Type"> <a class="reference internal" href="type.html#c.PyTypeObject" title="PyTypeObject">PyTypeObject</a> <code class="descname">PyBytes_Type</code><a class="headerlink" href="#c.PyBytes_Type" title="Permalink to this definition">¶</a></dt> <dd><p>This instance of <a class="reference internal" href="type.html#c.PyTypeObject" title="PyTypeObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyTypeObject</span></code></a> represents the Python bytes type; it is the same object as <a class="reference internal" href="../library/stdtypes.html#bytes" title="bytes"><code class="xref py py-class docutils literal notranslate"><span class="pre">bytes</span></code></a> in the Python layer.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_Check"> int <code class="descname">PyBytes_Check</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_Check" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if the object <em>o</em> is a bytes object or an instance of a subtype of the bytes type.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_CheckExact"> int <code class="descname">PyBytes_CheckExact</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_CheckExact" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if the object <em>o</em> is a bytes object, but not an instance of a subtype of the bytes type.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_FromString"> <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">PyBytes_FromString</code><span class="sig-paren">(</span>const char<em> *v</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_FromString" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new bytes object with a copy of the string <em>v</em> as value on success, and <em>NULL</em> on failure. The parameter <em>v</em> must not be <em>NULL</em>; it will not be checked.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_FromStringAndSize"> <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">PyBytes_FromStringAndSize</code><span class="sig-paren">(</span>const char<em> *v</em>, Py_ssize_t<em> len</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_FromStringAndSize" title="Permalink to this definition">¶</a></dt> <dd><p>Return a new bytes object with a copy of the string <em>v</em> as value and length <em>len</em> on success, and <em>NULL</em> on failure. If <em>v</em> is <em>NULL</em>, the contents of the bytes object are uninitialized.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_FromFormat"> <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">PyBytes_FromFormat</code><span class="sig-paren">(</span>const char<em> *format</em>, ...<span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_FromFormat" title="Permalink to this definition">¶</a></dt> <dd><p>Take a C <code class="xref c c-func docutils literal notranslate"><span class="pre">printf()</span></code>-style <em>format</em> string and a variable number of arguments, calculate the size of the resulting Python bytes object and return a bytes object with the values formatted into it. The variable arguments must be C types and must correspond exactly to the format characters in the <em>format</em> string. The following format characters are allowed:</p> <table border="1" class="docutils"> <colgroup> <col width="29%" /> <col width="23%" /> <col width="48%" /> </colgroup> <thead valign="bottom"> <tr class="row-odd"><th class="head">Format Characters</th> <th class="head">Type</th> <th class="head">Comment</th> </tr> </thead> <tbody valign="top"> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%%</span></code></td> <td><em>n/a</em></td> <td>The literal % character.</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%c</span></code></td> <td>int</td> <td>A single byte, represented as a C int.</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%d</span></code></td> <td>int</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%d")</span></code>.</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%u</span></code></td> <td>unsigned int</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%u")</span></code>.</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%ld</span></code></td> <td>long</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%ld")</span></code>.</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%lu</span></code></td> <td>unsigned long</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%lu")</span></code>.</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%zd</span></code></td> <td>Py_ssize_t</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%zd")</span></code>.</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%zu</span></code></td> <td>size_t</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%zu")</span></code>.</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%i</span></code></td> <td>int</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%i")</span></code>.</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%x</span></code></td> <td>int</td> <td>Exactly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%x")</span></code>.</td> </tr> <tr class="row-even"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%s</span></code></td> <td>char*</td> <td>A null-terminated C character array.</td> </tr> <tr class="row-odd"><td><code class="xref py py-attr docutils literal notranslate"><span class="pre">%p</span></code></td> <td>void*</td> <td>The hex representation of a C pointer. Mostly equivalent to <code class="docutils literal notranslate"><span class="pre">printf("%p")</span></code> except that it is guaranteed to start with the literal <code class="docutils literal notranslate"><span class="pre">0x</span></code> regardless of what the platform’s <code class="docutils literal notranslate"><span class="pre">printf</span></code> yields.</td> </tr> </tbody> </table> <p>An unrecognized format character causes all the rest of the format string to be copied as-is to the result object, and any extra arguments discarded.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_FromFormatV"> <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">PyBytes_FromFormatV</code><span class="sig-paren">(</span>const char<em> *format</em>, va_list<em> vargs</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_FromFormatV" title="Permalink to this definition">¶</a></dt> <dd><p>Identical to <a class="reference internal" href="#c.PyBytes_FromFormat" title="PyBytes_FromFormat"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBytes_FromFormat()</span></code></a> except that it takes exactly two arguments.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_FromObject"> <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">PyBytes_FromObject</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_FromObject" title="Permalink to this definition">¶</a></dt> <dd><p>Return the bytes representation of object <em>o</em> that implements the buffer protocol.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_Size"> Py_ssize_t <code class="descname">PyBytes_Size</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_Size" title="Permalink to this definition">¶</a></dt> <dd><p>Return the length of the bytes in bytes object <em>o</em>.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_GET_SIZE"> Py_ssize_t <code class="descname">PyBytes_GET_SIZE</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_GET_SIZE" title="Permalink to this definition">¶</a></dt> <dd><p>Macro form of <a class="reference internal" href="#c.PyBytes_Size" title="PyBytes_Size"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBytes_Size()</span></code></a> but without error checking.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_AsString"> char* <code class="descname">PyBytes_AsString</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_AsString" title="Permalink to this definition">¶</a></dt> <dd><p>Return a pointer to the contents of <em>o</em>. The pointer refers to the internal buffer of <em>o</em>, which consists of <code class="docutils literal notranslate"><span class="pre">len(o)</span> <span class="pre">+</span> <span class="pre">1</span></code> bytes. The last byte in the buffer is always null, regardless of whether there are any other null bytes. The data must not be modified in any way, unless the object was just created using <code class="docutils literal notranslate"><span class="pre">PyBytes_FromStringAndSize(NULL,</span> <span class="pre">size)</span></code>. It must not be deallocated. If <em>o</em> is not a bytes object at all, <a class="reference internal" href="#c.PyBytes_AsString" title="PyBytes_AsString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBytes_AsString()</span></code></a> returns <em>NULL</em> and raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_AS_STRING"> char* <code class="descname">PyBytes_AS_STRING</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *string</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_AS_STRING" title="Permalink to this definition">¶</a></dt> <dd><p>Macro form of <a class="reference internal" href="#c.PyBytes_AsString" title="PyBytes_AsString"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBytes_AsString()</span></code></a> but without error checking.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_AsStringAndSize"> int <code class="descname">PyBytes_AsStringAndSize</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *obj</em>, char<em> **buffer</em>, Py_ssize_t<em> *length</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_AsStringAndSize" title="Permalink to this definition">¶</a></dt> <dd><p>Return the null-terminated contents of the object <em>obj</em> through the output variables <em>buffer</em> and <em>length</em>.</p> <p>If <em>length</em> is <em>NULL</em>, the bytes object may not contain embedded null bytes; if it does, the function returns <code class="docutils literal notranslate"><span class="pre">-1</span></code> and a <a class="reference internal" href="../library/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>The buffer refers to an internal buffer of <em>obj</em>, which includes an additional null byte at the end (not counted in <em>length</em>). The data must not be modified in any way, unless the object was just created using <code class="docutils literal notranslate"><span class="pre">PyBytes_FromStringAndSize(NULL,</span> <span class="pre">size)</span></code>. It must not be deallocated. If <em>obj</em> is not a bytes object at all, <a class="reference internal" href="#c.PyBytes_AsStringAndSize" title="PyBytes_AsStringAndSize"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyBytes_AsStringAndSize()</span></code></a> returns <code class="docutils literal notranslate"><span class="pre">-1</span></code> and raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>.</p> <div class="versionchanged"> <p><span class="versionmodified">Changed in version 3.5: </span>Previously, <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> was raised when embedded null bytes were encountered in the bytes object.</p> </div> </dd></dl> <dl class="function"> <dt id="c.PyBytes_Concat"> void <code class="descname">PyBytes_Concat</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> **bytes</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *newpart</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_Concat" title="Permalink to this definition">¶</a></dt> <dd><p>Create a new bytes object in <em>*bytes</em> containing the contents of <em>newpart</em> appended to <em>bytes</em>; the caller will own the new reference. The reference to the old value of <em>bytes</em> will be stolen. If the new object cannot be created, the old reference to <em>bytes</em> will still be discarded and the value of <em>*bytes</em> will be set to <em>NULL</em>; the appropriate exception will be set.</p> </dd></dl> <dl class="function"> <dt id="c.PyBytes_ConcatAndDel"> void <code class="descname">PyBytes_ConcatAndDel</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> **bytes</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *newpart</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyBytes_ConcatAndDel" title="Permalink to this definition">¶</a></dt> <dd><p>Create a new bytes object in <em>*bytes</em> containing the contents of <em>newpart</em> appended to <em>bytes</em>. This version decrements the reference count of <em>newpart</em>.</p> </dd></dl> <dl class="function"> <dt id="c._PyBytes_Resize"> int <code class="descname">_PyBytes_Resize</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> **bytes</em>, Py_ssize_t<em> newsize</em><span class="sig-paren">)</span><a class="headerlink" href="#c._PyBytes_Resize" title="Permalink to this definition">¶</a></dt> <dd><p>A way to resize a bytes object even though it is “immutable”. Only use this to build up a brand new bytes object; don’t use this if the bytes may already be known in other parts of the code. It is an error to call this function if the refcount on the input bytes object is not one. Pass the address of an existing bytes object as an lvalue (it may be written into), and the new size desired. On success, <em>*bytes</em> holds the resized bytes object and <code class="docutils literal notranslate"><span class="pre">0</span></code> is returned; the address in <em>*bytes</em> may differ from its input value. If the reallocation fails, the original bytes object at <em>*bytes</em> is deallocated, <em>*bytes</em> is set to <em>NULL</em>, <a class="reference internal" href="../library/exceptions.html#MemoryError" title="MemoryError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">MemoryError</span></code></a> is set, and <code class="docutils literal notranslate"><span class="pre">-1</span></code> is returned.</p> </dd></dl> </div> </div> </div> </div> <div class="sphinxsidebar" role="navigation" aria-label="main navigation"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="complex.html" title="previous chapter">Complex Number Objects</a></p> <h4>Next topic</h4> <p class="topless"><a href="bytearray.html" title="next chapter">Byte Array Objects</a></p> <div role="note" aria-label="source link"> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li> <a href="https://github.com/python/cpython/blob/3.6/Doc/c-api/bytes.rst" rel="nofollow">Show Source </a> </li> </ul> </div> </div> </div> <div class="clearer"></div> </div> <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" >index</a></li> <li class="right" > <a href="../py-modindex.html" title="Python Module Index" >modules</a> |</li> <li class="right" > <a href="bytearray.html" title="Byte Array Objects" >next</a> |</li> <li class="right" > <a href="complex.html" title="Complex Number Objects" >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" >Python/C API Reference Manual</a> »</li> <li class="nav-item nav-item-2"><a href="concrete.html" >Concrete Objects Layer</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="footer"> © <a href="../copyright.html">Copyright</a> 2001-2023, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="https://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Dec 18, 2023. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.7.6. </div> </body> </html>