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<span id="iterator"></span><h1>イテレータプロトコル (iterator protocol)<a class="headerlink" href="#iterator-protocol" title="このヘッドラインへのパーマリンク">¶</a></h1>

<p>イテレータを扱うための固有の関数は二つあります。</p>

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<dt id="c.PyIter_Check">

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>&nbsp;*o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyIter_Check" title="この定義へのパーマリンク">¶</a></dt>

<dd><p><em>o</em> がイテレータプロトコルをサポートする場合に真を返します。</p>

<dl class="function">

<dt id="c.PyIter_Next">

<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>&nbsp;*o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyIter_Next" title="この定義へのパーマリンク">¶</a></dt>

<dd><em class="refcount">Return value: New reference.</em><p>反復処理 <em>o</em> における次の値を返します。オブジェクトはイテレータでなければなりません (これをチェックするのは呼び出し側の責任です)。要素が何も残っていない場合は、例外がセットされていない状態で <em>NULL</em> を返します。要素を取り出す際にエラーが生じた場合は、<em>NULL</em> を返し、発生した例外を送出します。</p>

<p>イテレータの返す要素にわたって反復処理を行うループを書くと、C のコードは以下のようになるはずです:</p>

<div class="highlight-c"><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>

<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>

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