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<section id="iterator-protocol">
<span id="iterator"></span><h1>Iterator Protocol<a class="headerlink" href="#iterator-protocol" title="Link to this heading">¶</a></h1>
<p>There are two functions specifically for working with iterators.</p>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyIter_Check">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyIter_Check</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyIter_Check" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.8.</em><p>Return non-zero if the object <em>o</em> can be safely passed to
<a class="reference internal" href="#c.PyIter_Next" title="PyIter_Next"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyIter_Next()</span></code></a>, and <code class="docutils literal notranslate"><span class="pre">0</span></code> otherwise. This function always succeeds.</p>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyAIter_Check">
<span class="kt"><span class="pre">int</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyAIter_Check</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyAIter_Check" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Return non-zero if the object <em>o</em> provides the <code class="xref py py-class docutils literal notranslate"><span class="pre">AsyncIterator</span></code>
protocol, and <code class="docutils literal notranslate"><span class="pre">0</span></code> otherwise. This function always succeeds.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.10.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyIter_Next">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="sig-name descname"><span class="n"><span class="pre">PyIter_Next</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">o</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyIter_Next" title="Link to this definition">¶</a><br /></dt>
<dd><em class="refcount return_new_ref">Return value: New reference.</em><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a>.</em><p>Return the next value from the iterator <em>o</em>. The object must be an iterator
according to <a class="reference internal" href="#c.PyIter_Check" title="PyIter_Check"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyIter_Check()</span></code></a> (it is up to the caller to check this).
If there are no remaining values, returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> with no exception set.
If an error occurs while retrieving the item, returns <code class="docutils literal notranslate"><span class="pre">NULL</span></code> 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 notranslate"><div class="highlight"><pre><span></span><span class="n">PyObject</span><span class="w"> </span><span class="o">*</span><span class="n">iterator</span><span class="w"> </span><span class="o">=</span><span class="w"> </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="w"> </span><span class="o">*</span><span class="n">item</span><span class="p">;</span>
<span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">iterator</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">NULL</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="cm">/* propagate error */</span>
<span class="p">}</span>
<span class="k">while</span><span class="w"> </span><span class="p">((</span><span class="n">item</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">PyIter_Next</span><span class="p">(</span><span class="n">iterator</span><span class="p">)))</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="cm">/* do something with item */</span>
<span class="w"> </span><span class="p">...</span>
<span class="w"> </span><span class="cm">/* release reference when done */</span>
<span class="w"> </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="w"> </span><span class="p">(</span><span class="n">PyErr_Occurred</span><span class="p">())</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="cm">/* propagate error */</span>
<span class="p">}</span>
<span class="k">else</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="cm">/* continue doing useful work */</span>
<span class="p">}</span>
</pre></div>
</div>
<dl class="c type">
<dt class="sig sig-object c" id="c.PySendResult">
<span class="k"><span class="pre">type</span></span><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PySendResult</span></span></span><a class="headerlink" href="#c.PySendResult" title="Link to this definition">¶</a><br /></dt>
<dd><p>The enum value used to represent different results of <a class="reference internal" href="#c.PyIter_Send" title="PyIter_Send"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyIter_Send()</span></code></a>.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.10.</span></p>
</div>
</dd></dl>
<dl class="c function">
<dt class="sig sig-object c" id="c.PyIter_Send">
<a class="reference internal" href="#c.PySendResult" title="PySendResult"><span class="n"><span class="pre">PySendResult</span></span></a><span class="w"> </span><span class="sig-name descname"><span class="n"><span class="pre">PyIter_Send</span></span></span><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">iter</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">arg</span></span>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject"><span class="n"><span class="pre">PyObject</span></span></a><span class="w"> </span><span class="p"><span class="pre">*</span></span><span class="p"><span class="pre">*</span></span><span class="n"><span class="pre">presult</span></span><span class="sig-paren">)</span><a class="headerlink" href="#c.PyIter_Send" title="Link to this definition">¶</a><br /></dt>
<dd><em class="stableabi"> Part of the <a class="reference internal" href="stable.html#stable"><span class="std std-ref">Stable ABI</span></a> since version 3.10.</em><p>Sends the <em>arg</em> value into the iterator <em>iter</em>. Returns:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">PYGEN_RETURN</span></code> if iterator returns. Return value is returned via <em>presult</em>.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">PYGEN_NEXT</span></code> if iterator yields. Yielded value is returned via <em>presult</em>.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">PYGEN_ERROR</span></code> if iterator has raised and exception. <em>presult</em> is set to <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p></li>
</ul>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.10.</span></p>
</div>
</dd></dl>
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