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<div class="section" id="using-the-python-interpreter">
<span id="tut-using"></span><h1>2. 使用 Python 直譯器<a class="headerlink" href="#using-the-python-interpreter" title="本標題的永久連結">¶</a></h1>
<div class="section" id="invoking-the-interpreter">
<span id="tut-invoking"></span><h2>2.1. 啟動直譯器<a class="headerlink" href="#invoking-the-interpreter" title="本標題的永久連結">¶</a></h2>
<p>The Python interpreter is usually installed as <code class="file docutils literal notranslate"><span class="pre">/usr/local/bin/python3.7</span></code>
on those machines where it is available; putting <code class="file docutils literal notranslate"><span class="pre">/usr/local/bin</span></code> in your
Unix shell’s search path makes it possible to start it by typing the command:</p>
<div class="highlight-text notranslate"><div class="highlight"><pre><span></span>python3.7
</pre></div>
</div>
<p>能啟動 Python <a class="footnote-reference" href="#id2" id="id1">[1]</a>。因為直譯器存放的目錄是個安裝選項，其他的目錄也是有可能的；請洽談在地的 Python 達人或者系統管理員。（例如：<code class="file docutils literal notranslate"><span class="pre">/usr/local/python</span></code> 是個很常見的另類存放路徑。）</p>
<p>On Windows machines, the Python installation is usually placed in
<code class="file docutils literal notranslate"><span class="pre">C:\Python36</span></code>, though you can change this when you’re running the
installer. To add this directory to your path, you can type the following
command into the command prompt in a DOS box:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nb">set</span> <span class="n">path</span><span class="o">=%</span><span class="n">path</span><span class="o">%</span><span class="p">;</span><span class="n">C</span><span class="p">:</span>\<span class="n">python36</span>
</pre></div>
</div>
<p>在主提示符輸入一個 end-of-file 字元（在 Unix 上為 <kbd class="kbd docutils literal notranslate">Control-D</kbd>；在 Windows 上為 <kbd class="kbd docutils literal notranslate">Control-Z</kbd>）會使得直譯器以零退出狀況 (zero exit status) 離開。如果上述的做法沒有效，也可以輸入指令 <code class="docutils literal notranslate"><span class="pre">quit()</span></code> 離開直譯器。</p>
<p>直譯器的指令列編輯功能有很多，在支援 readline 函式庫的系統上包含：互動編輯、歷史取代、指令補完等功能。最快檢查有無支援 readline 的方法為在第一個 Python 提示符後輸入 <kbd class="kbd docutils literal notranslate">Control-P</kbd>，如果出現嗶嗶聲，就代表有支援；見附錄 <a class="reference internal" href="interactive.html#tut-interacting"><span class="std std-ref">Interactive Input Editing and History Substitution</span></a> 介紹相關的快速鍵。如果什麼事沒有發生，或者出現一個 <code class="docutils literal notranslate"><span class="pre">^P</span></code>，就代表並沒有這指令列編輯功能；此時只能使用 backspace 去除該行的字元。</p>
<p>這個直譯器使用起來像是 Unix shell：如果它被呼叫時連結至一個 tty 裝置，它會互動式地讀取並執行指令；如果被呼叫時給定檔名為引數或者使用 stdin 傳入檔案內容，它會將這個檔案視為<strong>腳本</strong>來閱讀。</p>
<p>另一個起動直譯器的方式為 <code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">-c</span> <span class="pre">command</span> <span class="pre">[arg]</span> <span class="pre">...</span></code>，它會執行在 <em>command</em> 裡的指令（們），行為如同 shell 的 <a class="reference internal" href="../using/cmdline.html#cmdoption-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> 選項。因為 Python 的指令包含空白等 shell 用到的特殊字元，通常建議用單引號把 <em>command</em> 包起來。</p>
<p>有些 Python 模組使用上如腳本般一樣方便。透過 <code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">-m</span> <span class="pre">module</span> <span class="pre">[arg]</span> <span class="pre">...</span></code> 可以執行 <em>module</em> 模組的原始碼，就如同直接傳入那個模組的完整路徑一樣的行為。</p>
<p>當要執行一個腳本檔時，有時候會希望在腳本結束時進入互動模式。此時可在執行腳本的指令加入 <a class="reference internal" href="../using/cmdline.html#cmdoption-i"><code class="xref std std-option docutils literal notranslate"><span class="pre">-i</span></code></a>。</p>
<p>所有指令可用的參數都詳記在<a class="reference internal" href="../using/cmdline.html#using-on-general"><span class="std std-ref">Command line and environment</span></a>。</p>
<div class="section" id="argument-passing">
<span id="tut-argpassing"></span><h3>2.1.1. 傳遞引數<a class="headerlink" href="#argument-passing" title="本標題的永久連結">¶</a></h3>
<p>當直擇器收到腳本的名稱和額外的引數後，他們會轉換為由字串所組成的 list（串列）並指派給 <code class="docutils literal notranslate"><span class="pre">sys</span></code> 模組的 <code class="docutils literal notranslate"><span class="pre">argv</span></code> 變數。你可以執行 <code class="docutils literal notranslate"><span class="pre">import</span> <span class="pre">sys</span></code> 取得這個串列。這個串列的長度至少為一；當沒有給任何腳本名稱和引數時， <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> 為空字串。當腳本名為 <code class="docutils literal notranslate"><span class="pre">'-'</span></code>（指標準輸入）時， <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> 為 <code class="docutils literal notranslate"><span class="pre">'-'</span></code>。當使用 <a class="reference internal" href="../using/cmdline.html#cmdoption-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> <em>command</em> 時， <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> 為 <code class="docutils literal notranslate"><span class="pre">'-c'</span></code>。當使用 <a class="reference internal" href="../using/cmdline.html#cmdoption-m"><code class="xref std std-option docutils literal notranslate"><span class="pre">-m</span></code></a> <em>module</em> 時， <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> 為該模組存在的完整路徑。其餘非 <a class="reference internal" href="../using/cmdline.html#cmdoption-c"><code class="xref std std-option docutils literal notranslate"><span class="pre">-c</span></code></a> <em>command</em> 或 <a class="reference internal" href="../using/cmdline.html#cmdoption-m"><code class="xref std std-option docutils literal notranslate"><span class="pre">-m</span></code></a> <em>module</em> 的選項不會被 Python 直譯器吸收掉，而是留在 <code class="docutils literal notranslate"><span class="pre">sys.argv</span></code> 變數中給後續的 command 或 module 使用。</p>
</div>
<div class="section" id="interactive-mode">
<span id="tut-interactive"></span><h3>2.1.2. 互動模式<a class="headerlink" href="#interactive-mode" title="本標題的永久連結">¶</a></h3>
<p>When commands are read from a tty, the interpreter is said to be in <em>interactive
mode</em>. In this mode it prompts for the next command with the <em>primary prompt</em>,
usually three greater-than signs (<code class="docutils literal notranslate"><span class="pre">>>></span></code>); for continuation lines it prompts
with the <em>secondary prompt</em>, by default three dots (<code class="docutils literal notranslate"><span class="pre">...</span></code>). The interpreter
prints a welcome message stating its version number and a copyright notice
before printing the first prompt:</p>
<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> python3.7
<span class="go">Python 3.7 (default, Sep 16 2015, 09:25:04)</span>
<span class="go">[GCC 4.8.2] on linux</span>
<span class="go">Type "help", "copyright", "credits" or "license" for more information.</span>
<span class="gp">></span>>>
</pre></div>
</div>
<p>接續多行的情況出現在需要多行才能建立完整指令時。舉例來說，像是 <a class="reference internal" href="../reference/compound_stmts.html#if"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">if</span></code></a> 敘述：</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">the_world_is_flat</span> <span class="o">=</span> <span class="kc">True</span>
<span class="gp">>>> </span><span class="k">if</span> <span class="n">the_world_is_flat</span><span class="p">:</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="s2">"Be careful not to fall off!"</span><span class="p">)</span>
<span class="gp">...</span>
<span class="go">Be careful not to fall off!</span>
</pre></div>
</div>
<p>更多有關互動模式的使用，請見<a class="reference internal" href="appendix.html#tut-interac"><span class="std std-ref">互動模式</span></a>。</p>
</div>
</div>
<div class="section" id="the-interpreter-and-its-environment">
<span id="tut-interp"></span><h2>2.2. 直譯器與它的環境<a class="headerlink" href="#the-interpreter-and-its-environment" title="本標題的永久連結">¶</a></h2>
<div class="section" id="source-code-encoding">
<span id="tut-source-encoding"></span><h3>2.2.1. 原始碼的字元編碼 (encoding)<a class="headerlink" href="#source-code-encoding" title="本標題的永久連結">¶</a></h3>
<p>預設 Python 原始碼檔案的字元編碼使用 UTF-8。在這個編碼中，世界上多數語言的文字可以同時被使用在字串內容、識別名 (identifier) 及註解中 — 雖然在標準函式庫中只使用 ASCII 字元作為識別名，這也是個任何 portable 程式碼需遵守的慣例。如果要正確地顯示所有字元，您的編輯器需要能夠認識檔案為 UTF-8，並且需要能顯示檔案中所有字元的字型。</p>
<p>To declare an encoding other than the default one, a special comment line
should be added as the <em>first</em> line of the file. The syntax is as follows:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="c1"># -*- coding: encoding -*-</span>
</pre></div>
</div>
<p>where <em>encoding</em> is one of the valid <a class="reference internal" href="../library/codecs.html#module-codecs" title="codecs: Encode and decode data and streams."><code class="xref py py-mod docutils literal notranslate"><span class="pre">codecs</span></code></a> supported by Python.</p>
<p>For example, to declare that Windows-1252 encoding is to be used, the first
line of your source code file should be:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="c1"># -*- coding: cp1252 -*-</span>
</pre></div>
</div>
<p>One exception to the <em>first line</em> rule is when the source code starts with a
<a class="reference internal" href="appendix.html#tut-scripts"><span class="std std-ref">UNIX 「shebang」 line</span></a>. In this case, the encoding
declaration should be added as the second line of the file. For example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/env python3</span>
<span class="c1"># -*- coding: cp1252 -*-</span>
</pre></div>
</div>
<p class="rubric">註解</p>
<table class="docutils footnote" frame="void" id="id2" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>在 Unix 中，Python 3.x 直譯器預設安裝不會以 <code class="docutils literal notranslate"><span class="pre">python</span></code> 作為執行檔名稱，以避免與 現有的 Python 2.x 執行檔名稱衝突。</td></tr>
</tbody>
</table>
</div>
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<li><a class="reference internal" href="#invoking-the-interpreter">2.1. 啟動直譯器</a><ul>
<li><a class="reference internal" href="#argument-passing">2.1.1. 傳遞引數</a></li>
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