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<title>python中 __（双下划线）的作用 · Tugqi Biz
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<h1><a href="http://wbowam.github.io/pythonzhong-__shuang-xia-hua-xian-de-zuo-yong.html"> python中 __（双下划线）的作用 </a></h1>
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<p>Python中默认的成员函数，成员变量都是公开的(public),而且python中没有类似public,private等关键词来修饰成员函数，成员变量。 </p>
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<p>可有时候需要用到私有变量，因此诞生了__。 </p>
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<p>变量名或函数名前加上 ”__“两个下划线，那么这个函数或变量就会为私有的了。</p>
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<p>私有意味着只有内部能使用，对外部隐藏。 </p>
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<li>
<p>在内部，python使用一种 name mangling 技术，将 __membername替换成 _classname__membername来使用。 <br />
在外部，使用原来的私有成员的名字时，会提示找不到。（达到了隐藏的效果） </p>
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<hr />
<div class="highlight"><pre><span class="n">class</span> <span class="n">Tester</span><span class="p">(</span><span class="n">object</span><span class="p">)</span><span class="o">:</span>
<span class="n">__foo</span> <span class="o">=</span> <span class="s">"hi"</span>
<span class="o">>>></span> <span class="n">t</span> <span class="o">=</span> <span class="n">Tester</span><span class="p">()</span>
<span class="o">>>></span> <span class="n">t</span><span class="p">.</span><span class="n">_Tester__foo</span>
<span class="err">'</span><span class="n">hi</span><span class="err">'</span>
</pre></div>
<div class="highlight"><pre><span class="n">class</span> <span class="n">Tester</span><span class="p">(</span><span class="n">object</span><span class="p">)</span><span class="o">:</span>
<span class="p">...</span> <span class="n">def</span> <span class="n">__init__</span><span class="p">(</span><span class="n">self</span><span class="p">)</span><span class="o">:</span>
<span class="p">...</span> <span class="n">self</span><span class="p">.</span><span class="n">__foo</span> <span class="o">=</span> <span class="s">"hi"</span>
<span class="p">...</span>
<span class="o">>>></span> <span class="n">t</span><span class="o">=</span><span class="n">Tester</span><span class="p">()</span>
<span class="o">>>></span><span class="n">t</span><span class="p">.</span><span class="n">_Tester__foo</span>
<span class="err">'</span><span class="n">hi</span><span class="err">'</span>
</pre></div>
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<h4>Published</h4>
<time pubdate="pubdate" datetime="2014-07-07T00:00:00+08:00">Jul 7, 2014</time>
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<a class="category-link" href="/categories.html#It-ref">It</a>
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