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<div class="section" id="iterator-protocol">
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<span id="iterator"></span><h1>Iterator Protocol<a class="headerlink" href="#iterator-protocol" title="Permalink to this headline">¶</a></h1>
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<p>There are two functions specifically for working with iterators.</p>
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<dl class="function">
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<dt id="c.PyIter_Check">
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int <code class="descname">PyIter_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.PyIter_Check" title="Permalink to this definition">¶</a></dt>
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<dd><p>Return true if the object <em>o</em> supports the iterator protocol.</p>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyIter_Next">
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<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="descname">PyIter_Next</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.PyIter_Next" title="Permalink to this definition">¶</a></dt>
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<dd><em class="refcount">Return value: New reference.</em><p>Return the next value from the iteration <em>o</em>. The object must be an iterator
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(it is up to the caller to check this). If there are no remaining values,
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returns <em>NULL</em> with no exception set. If an error occurs while retrieving
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the item, returns <em>NULL</em> and passes along the exception.</p>
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</dd></dl>
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<p>To write a loop which iterates over an iterator, the C code should look
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something like this:</p>
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<div class="highlight-c notranslate"><div class="highlight"><pre><span></span><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>
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<span class="n">PyObject</span> <span class="o">*</span><span class="n">item</span><span class="p">;</span>
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<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>
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<span class="cm">/* propagate error */</span>
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<span class="p">}</span>
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<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>
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<span class="cm">/* do something with item */</span>
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<span class="p">...</span>
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<span class="cm">/* release reference when done */</span>
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<span class="n">Py_DECREF</span><span class="p">(</span><span class="n">item</span><span class="p">);</span>
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<span class="p">}</span>
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<span class="n">Py_DECREF</span><span class="p">(</span><span class="n">iterator</span><span class="p">);</span>
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<span class="k">if</span> <span class="p">(</span><span class="n">PyErr_Occurred</span><span class="p">())</span> <span class="p">{</span>
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<span class="cm">/* propagate error */</span>
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<span class="p">}</span>
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<span class="k">else</span> <span class="p">{</span>
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<span class="cm">/* continue doing useful work */</span>
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<span class="p">}</span>
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</pre></div>
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title="previous chapter">Mapping Protocol</a></p>
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<br />
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Last updated on Jul 13, 2019.
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