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<section id="appendix">
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<span id="tut-appendix"></span><h1><span class="section-number">16. </span>附录<a class="headerlink" href="#appendix" title="永久链接至标题">¶</a></h1>
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<section id="interactive-mode">
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<span id="tut-interac"></span><h2><span class="section-number">16.1. </span>交互模式<a class="headerlink" href="#interactive-mode" title="永久链接至标题">¶</a></h2>
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<section id="error-handling">
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<span id="tut-error"></span><h3><span class="section-number">16.1.1. </span>错误处理<a class="headerlink" href="#error-handling" title="永久链接至标题">¶</a></h3>
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<p>当发生错误时，解释器会打印错误信息和错误堆栈。在交互模式下，将返回到主命令提示符；如果输入内容来自文件，在打印错误堆栈之后，程序会以非零状态退出。（这里所说的错误不包括 <a class="reference internal" href="../reference/compound_stmts.html#try"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">try</span></code></a> 语句中由 <a class="reference internal" href="../reference/compound_stmts.html#except"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">except</span></code></a> 所捕获的异常。）有些错误是无条件致命的，会导致程序以非零状态退出；比如内部逻辑矛盾或内存耗尽。所有错误信息都会被写入标准错误流；而命令的正常输出则被写入标准输出流。</p>
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<p>将中断字符（通常为 <kbd class="kbd docutils literal notranslate">Control-C</kbd> 或 <kbd class="kbd docutils literal notranslate">Delete</kbd> ）键入主要或辅助提示会取消输入并返回主提示符。 <a class="footnote-reference brackets" href="#id2" id="id1">1</a> 在执行命令时键入中断引发的 <a class="reference internal" href="../library/exceptions.html#KeyboardInterrupt" title="KeyboardInterrupt"><code class="xref py py-exc docutils literal notranslate"><span class="pre">KeyboardInterrupt</span></code></a> 异常，可以由 <a class="reference internal" href="../reference/compound_stmts.html#try"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">try</span></code></a> 语句处理。</p>
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</section>
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<section id="executable-python-scripts">
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<span id="tut-scripts"></span><h3><span class="section-number">16.1.2. </span>可执行的Python脚本<a class="headerlink" href="#executable-python-scripts" title="永久链接至标题">¶</a></h3>
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<p>在BSD等类Unix系统上，Python脚本可以直接执行，就像shell脚本一样，第一行添加:</p>
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<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/env python3.5</span>
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</pre></div>
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</div>
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<p>（假设解释器位于用户的 <span class="target" id="index-4"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PATH</span></code> ）脚本的开头，并将文件设置为可执行。 <code class="docutils literal notranslate"><span class="pre">#!</span></code> 必须是文件的前两个字符。在某些平台上，第一行必须以Unix样式的行结尾（<code class="docutils literal notranslate"><span class="pre">'\n'</span></code>）结束，而不是以Windows（<code class="docutils literal notranslate"><span class="pre">'\r\n'</span></code>）行结尾。请注意，散列或磅字符 <code class="docutils literal notranslate"><span class="pre">'#'</span></code> 在Python中代表注释开始。</p>
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<p>可以使用 <strong class="program">chmod</strong> 命令为脚本提供可执行模式或权限。</p>
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<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>chmod<span class="w"> </span>+x<span class="w"> </span>myscript.py
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</pre></div>
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</div>
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<p>在Windows系统上，没有“可执行模式”的概念。 Python安装程序自动将 <code class="docutils literal notranslate"><span class="pre">.py</span></code> 文件与 <code class="docutils literal notranslate"><span class="pre">python.exe</span></code> 相关联，这样双击Python文件就会将其作为脚本运行。扩展也可以是 <code class="docutils literal notranslate"><span class="pre">.pyw</span></code> ，在这种情况下，会隐藏通常出现的控制台窗口。</p>
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</section>
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<section id="the-interactive-startup-file">
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<span id="tut-startup"></span><h3><span class="section-number">16.1.3. </span>交互式启动文件<a class="headerlink" href="#the-interactive-startup-file" title="永久链接至标题">¶</a></h3>
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<p>当您以交互方式使用Python时，每次启动解释器时都会执行一些标准命令，这通常很方便。您可以通过将名为 <span class="target" id="index-5"></span><a class="reference internal" href="../using/cmdline.html#envvar-PYTHONSTARTUP"><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PYTHONSTARTUP</span></code></a> 的环境变量设置为包含启动命令的文件名来实现。这类似于Unix shell的 <code class="file docutils literal notranslate"><span class="pre">.profile</span></code> 功能。</p>
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<p>This file is only read in interactive sessions, not when Python reads commands
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from a script, and not when <code class="file docutils literal notranslate"><span class="pre">/dev/tty</span></code> is given as the explicit source of
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commands (which otherwise behaves like an interactive session). It is executed
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in the same namespace where interactive commands are executed, so that objects
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that it defines or imports can be used without qualification in the interactive
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session. You can also change the prompts <code class="docutils literal notranslate"><span class="pre">sys.ps1</span></code> and <code class="docutils literal notranslate"><span class="pre">sys.ps2</span></code> in this
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file.</p>
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<p>如果你想从当前目录中读取一个额外的启动文件，你可以使用像 <code class="docutils literal notranslate"><span class="pre">if</span> <span class="pre">os.path.isfile('.pythonrc.py'):</span> <span class="pre">exec(open('.pythonrc.py').read())</span></code> 这样的代码在全局启动文件中对它进行编程。如果要在脚本中使用启动文件，则必须在脚本中显式执行此操作:</p>
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<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">os</span>
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<span class="n">filename</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">environ</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s1">'PYTHONSTARTUP'</span><span class="p">)</span>
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<span class="k">if</span> <span class="n">filename</span> <span class="ow">and</span> <span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">isfile</span><span class="p">(</span><span class="n">filename</span><span class="p">):</span>
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<span class="k">with</span> <span class="nb">open</span><span class="p">(</span><span class="n">filename</span><span class="p">)</span> <span class="k">as</span> <span class="n">fobj</span><span class="p">:</span>
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<span class="n">startup_file</span> <span class="o">=</span> <span class="n">fobj</span><span class="o">.</span><span class="n">read</span><span class="p">()</span>
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<span class="n">exec</span><span class="p">(</span><span class="n">startup_file</span><span class="p">)</span>
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</pre></div>
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</div>
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</section>
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<section id="the-customization-modules">
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<span id="tut-customize"></span><h3><span class="section-number">16.1.4. </span>定制模块<a class="headerlink" href="#the-customization-modules" title="永久链接至标题">¶</a></h3>
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||
<p>Python提供了两个钩子来让你自定义它：<code class="xref py py-mod docutils literal notranslate"><span class="pre">sitecustomize</span></code> 和 <code class="xref py py-mod docutils literal notranslate"><span class="pre">usercustomize</span></code>。要查看其工作原理，首先需要找到用户site-packages目录的位置。启动Python并运行此代码:</p>
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<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">site</span>
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<span class="gp">>>> </span><span class="n">site</span><span class="o">.</span><span class="n">getusersitepackages</span><span class="p">()</span>
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<span class="go">'/home/user/.local/lib/python3.5/site-packages'</span>
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</pre></div>
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</div>
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<p>现在，您可以在该目录中创建一个名为 <code class="file docutils literal notranslate"><span class="pre">usercustomize.py</span></code> 的文件，并将所需内容放入其中。它会影响Python的每次启动，除非它以 <a class="reference internal" href="../using/cmdline.html#cmdoption-s"><code class="xref std std-option docutils literal notranslate"><span class="pre">-s</span></code></a> 选项启动，以禁用自动导入。</p>
|
||
<p><code class="xref py py-mod docutils literal notranslate"><span class="pre">sitecustomize</span></code> 以相同的方式工作，但通常由计算机管理员在全局 site-packages 目录中创建，并在 <code class="xref py py-mod docutils literal notranslate"><span class="pre">usercustomize</span></code> 之前被导入。有关详情请参阅 <a class="reference internal" href="../library/site.html#module-site" title="site: Module responsible for site-specific configuration."><code class="xref py py-mod docutils literal notranslate"><span class="pre">site</span></code></a> 模块的文档。</p>
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<p class="rubric">备注</p>
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<dl class="footnote brackets">
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<dt class="label" id="id2"><span class="brackets"><a class="fn-backref" href="#id1">1</a></span></dt>
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<dd><p>GNU Readline 包的问题可能会阻止这种情况。</p>
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</dd>
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</dl>
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</section>
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</section>
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</section>
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<div class="sphinxsidebarwrapper">
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<h3><a href="../contents.html">目录</a></h3>
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<ul>
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<li><a class="reference internal" href="#">16. 附录</a><ul>
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<li><a class="reference internal" href="#interactive-mode">16.1. 交互模式</a><ul>
|
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<li><a class="reference internal" href="#error-handling">16.1.1. 错误处理</a></li>
|
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<li><a class="reference internal" href="#executable-python-scripts">16.1.2. 可执行的Python脚本</a></li>
|
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<li><a class="reference internal" href="#the-interactive-startup-file">16.1.3. 交互式启动文件</a></li>
|
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<li><a class="reference internal" href="#the-customization-modules">16.1.4. 定制模块</a></li>
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