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<section id="weak-reference-objects">
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<span id="weakrefobjects"></span><h1>弱引用对象<a class="headerlink" href="#weak-reference-objects" title="永久链接至标题">¶</a></h1>
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<p>Python 支持 “弱引用” 作为一类对象。具体来说，有两种直接实现弱引用的对象。第一种就是简单的引用对象，第二种尽可能地作用为一个原对象的代理。</p>
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<dl class="function">
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<dt id="c.PyWeakref_Check">
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int <code class="sig-name descname">PyWeakref_Check</code><span class="sig-paren">(</span>ob<span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_Check" title="永久链接至目标">¶</a></dt>
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<dd><p>如果 “ob” 是一个引用或者一个代理对象，则返回 true。</p>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyWeakref_CheckRef">
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int <code class="sig-name descname">PyWeakref_CheckRef</code><span class="sig-paren">(</span>ob<span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_CheckRef" title="永久链接至目标">¶</a></dt>
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<dd><p>如果 “ob” 是一个引用，则返回 true。</p>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyWeakref_CheckProxy">
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int <code class="sig-name descname">PyWeakref_CheckProxy</code><span class="sig-paren">(</span>ob<span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_CheckProxy" title="永久链接至目标">¶</a></dt>
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<dd><p>如果 “ob” 是一个代理对象，则返回 true。</p>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyWeakref_NewRef">
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<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyWeakref_NewRef</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *ob</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *callback</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_NewRef" title="永久链接至目标">¶</a></dt>
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<dd><em class="refcount">Return value: New reference.</em><p>返回对象 <em>ob</em> 的一个弱引用对象。 该函数总是会返回一个新引用，但不保证创建一个新的对象；它有可能返回一个现有的引用对象。 第二个形参 <em>callback</em> 为一个可调用对象，它会在 <em>ob</em> 被作为垃圾回收时接收通知；它应该接受一个单独形参，即弱引用对象本身。 <em>callback</em> 也可以为 <code class="docutils literal notranslate"><span class="pre">None</span></code> 或 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。 如果 <em>ob</em> 不是一个弱引用对象，或者如果 <em>callback</em> 不是可调用对象，<code class="docutils literal notranslate"><span class="pre">None</span></code> 或 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，该函数将返回 <code class="docutils literal notranslate"><span class="pre">NULL</span></code> 并且引发 <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>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyWeakref_NewProxy">
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<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyWeakref_NewProxy</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *ob</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *callback</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_NewProxy" title="永久链接至目标">¶</a></dt>
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<dd><em class="refcount">Return value: New reference.</em><p>返回对象 <em>ob</em> 的一个弱引用代理对象。 该函数将总是返回一个新的引用，但不保证创建一个新的对象；它有可能返回一个现有的代理对象。 第二个形参 <em>callback</em> 为一个可调用对象，它会在 <em>ob</em> 被作为垃圾回收时接收通知；它应该接受一个单独形参，即弱引用对象本身。 <em>callback</em> 也可以为 <code class="docutils literal notranslate"><span class="pre">None</span></code> 或 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>。 如果 <em>ob</em> 不是一个弱引用对象，或者如果 <em>callback</em> 不是可调用对象，<code class="docutils literal notranslate"><span class="pre">None</span></code> 或 <code class="docutils literal notranslate"><span class="pre">NULL</span></code>，该函数将返回 <code class="docutils literal notranslate"><span class="pre">NULL</span></code> 并且引发 <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>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyWeakref_GetObject">
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<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyWeakref_GetObject</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *ref</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_GetObject" title="永久链接至目标">¶</a></dt>
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<dd><em class="refcount">Return value: Borrowed reference.</em><p>返回弱引用对象 ref 的被引用对象。如果被引用对象不再存在，则返回 <code class="xref py py-const docutils literal notranslate"><span class="pre">Py_None</span></code>。</p>
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<div class="admonition note">
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<p class="admonition-title">注解</p>
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<p>该函数返回被引用对象的一个**借来的引用**。这意味着除非你很清楚在你使用期间这个对象不可能被销毁，否则你应该始终对该对象调用 <a class="reference internal" href="refcounting.html#c.Py_INCREF" title="Py_INCREF"><code class="xref c c-func docutils literal notranslate"><span class="pre">Py_INCREF()</span></code></a>。</p>
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</dd></dl>
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<dl class="function">
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<dt id="c.PyWeakref_GET_OBJECT">
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<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PyWeakref_GET_OBJECT</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *ref</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PyWeakref_GET_OBJECT" title="永久链接至目标">¶</a></dt>
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<dd><em class="refcount">Return value: Borrowed reference.</em><p>类似 <a class="reference internal" href="#c.PyWeakref_GetObject" title="PyWeakref_GetObject"><code class="xref c c-func docutils literal notranslate"><span class="pre">PyWeakref_GetObject()</span></code></a>，但实现为一个不做类型检查的宏。</p>
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