Edit File: iter.html
<!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="Content-Type" content="text/html; charset=utf-8" /> <title>Iterator Protocol — Python 2.7.5 documentation</title> <link rel="stylesheet" href="../_static/default.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '2.7.5', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </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 2.7.5 documentation" href="../_static/opensearch.xml"/> <link rel="author" title="About these documents" href="../about.html" /> <link rel="copyright" title="Copyright" href="../copyright.html" /> <link rel="top" title="Python 2.7.5 documentation" href="../index.html" /> <link rel="up" title="Abstract Objects Layer" href="abstract.html" /> <link rel="next" title="Old Buffer Protocol" href="objbuffer.html" /> <link rel="prev" title="Mapping Protocol" href="mapping.html" /> <link rel="shortcut icon" type="image/png" href="../_static/py.png" /> <script type="text/javascript" src="../_static/copybutton.js"></script> </head> <body> <div class="related"> <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="objbuffer.html" title="Old Buffer Protocol" accesskey="N">next</a> |</li> <li class="right" > <a href="mapping.html" title="Mapping Protocol" accesskey="P">previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >Python/C API Reference Manual</a> »</li> <li><a href="abstract.html" accesskey="U">Abstract Objects Layer</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="iterator-protocol"> <span id="iterator"></span><h1>Iterator Protocol<a class="headerlink" href="#iterator-protocol" title="Permalink to this headline">¶</a></h1> <p class="versionadded"> <span class="versionmodified">New in version 2.2.</span></p> <p>There are only a couple of functions specifically for working with iterators.</p> <dl class="function"> <dt id="PyIter_Check"> int <tt class="descname">PyIter_Check</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *o</em><big>)</big><a class="headerlink" href="#PyIter_Check" title="Permalink to this definition">¶</a></dt> <dd><p>Return true if the object <em>o</em> supports the iterator protocol.</p> </dd></dl> <dl class="function"> <dt id="PyIter_Next"> <a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a>* <tt class="descname">PyIter_Next</tt><big>(</big><a class="reference internal" href="structures.html#PyObject" title="PyObject">PyObject</a><em> *o</em><big>)</big><a class="headerlink" href="#PyIter_Next" title="Permalink to this definition">¶</a></dt> <dd><em class="refcount">Return value: New reference.</em><p>Return the next value from the iteration <em>o</em>. If the object is an iterator, this retrieves the next value from the iteration, and returns <em>NULL</em> with no exception set if there are no remaining items. If the object is not an iterator, <a class="reference internal" href="../library/exceptions.html#exceptions.TypeError" title="exceptions.TypeError"><tt class="xref py py-exc docutils literal"><span class="pre">TypeError</span></tt></a> is raised, or if there is an error in retrieving the item, returns <em>NULL</em> and passes along the exception.</p> </dd></dl> <p>To write a loop which iterates over an iterator, the C code should look something like this:</p> <div class="highlight-c"><div class="highlight"><pre><span class="n">PyObject</span> <span class="o">*</span><span class="n">iterator</span> <span class="o">=</span> <span class="n">PyObject_GetIter</span><span class="p">(</span><span class="n">obj</span><span class="p">);</span> <span class="n">PyObject</span> <span class="o">*</span><span class="n">item</span><span class="p">;</span> <span class="k">if</span> <span class="p">(</span><span class="n">iterator</span> <span class="o">==</span> <span class="nb">NULL</span><span class="p">)</span> <span class="p">{</span> <span class="cm">/* propagate error */</span> <span class="p">}</span> <span class="k">while</span> <span class="p">(</span><span class="n">item</span> <span class="o">=</span> <span class="n">PyIter_Next</span><span class="p">(</span><span class="n">iterator</span><span class="p">))</span> <span class="p">{</span> <span class="cm">/* do something with item */</span> <span class="p">...</span> <span class="cm">/* release reference when done */</span> <span class="n">Py_DECREF</span><span class="p">(</span><span class="n">item</span><span class="p">);</span> <span class="p">}</span> <span class="n">Py_DECREF</span><span class="p">(</span><span class="n">iterator</span><span class="p">);</span> <span class="k">if</span> <span class="p">(</span><span class="n">PyErr_Occurred</span><span class="p">())</span> <span class="p">{</span> <span class="cm">/* propagate error */</span> <span class="p">}</span> <span class="k">else</span> <span class="p">{</span> <span class="cm">/* continue doing useful work */</span> <span class="p">}</span> </pre></div> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h4>Previous topic</h4> <p class="topless"><a href="mapping.html" title="previous chapter">Mapping Protocol</a></p> <h4>Next topic</h4> <p class="topless"><a href="objbuffer.html" title="next chapter">Old Buffer Protocol</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="../bugs.html">Report a Bug</a></li> <li><a href="../_sources/c-api/iter.txt" rel="nofollow">Show Source</a></li> </ul> <div id="searchbox" style="display: none"> <h3>Quick search</h3> <form class="search" action="../search.html" method="get"> <input 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> <p class="searchtip" style="font-size: 90%"> Enter search terms or a module, class or function name. </p> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </div> </div> <div class="clearer"></div> </div> <div class="related"> <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="objbuffer.html" title="Old Buffer Protocol" >next</a> |</li> <li class="right" > <a href="mapping.html" title="Mapping Protocol" >previous</a> |</li> <li><img src="../_static/py.png" alt="" style="vertical-align: middle; margin-top: -1px"/></li> <li><a href="http://www.python.org/">Python</a> »</li> <li> <a href="../index.html">Python 2.7.5 documentation</a> » </li> <li><a href="index.html" >Python/C API Reference Manual</a> »</li> <li><a href="abstract.html" >Abstract Objects Layer</a> »</li> </ul> </div> <div class="footer"> © <a href="../copyright.html">Copyright</a> 1990-2020, Python Software Foundation. <br /> The Python Software Foundation is a non-profit corporation. <a href="http://www.python.org/psf/donations/">Please donate.</a> <br /> Last updated on Oct 13, 2020. <a href="../bugs.html">Found a bug</a>? <br /> Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.1.3. </div> </body> </html>