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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>16. 附錄 — Python 3.7.0 說明文件</title>

title="在 Python 3.7.0 說明文件中搜尋"

href="../_static/opensearch.xml"/>

</head><body>

<ul>

<a href="../genindex.html" title="General Index"

accesskey="I">索引</a></li>

<a href="../py-modindex.html" title="Python 模組索引"

>模組</a> |</li>

<a href="../using/index.html" title="Python Setup and Usage"

accesskey="N">下一頁</a> |</li>

<a href="floatingpoint.html" title="15. Floating Point Arithmetic: Issues and Limitations"

accesskey="P">上一頁</a> |</li>

<li><img src="../_static/py.png" alt=""

style="vertical-align: middle; margin-top: -1px"/></li>

<li><a href="https://www.python.org/">Python</a> »</li>

<li>

<a href="../index.html">Documentation </a> »

</li>

<li class="nav-item nav-item-1"><a href="index.html" accesskey="U">Python 教學</a> »</li>

</form>

</div>

</li>

</ul>

</div>

<span id="tut-error"></span><h3>16.1.1. Error Handling<a class="headerlink" href="#error-handling" title="本標題的永久連結">¶</a></h3>

<p>When an error occurs, the interpreter prints an error message and a stack trace.

In interactive mode, it then returns to the primary prompt; when input came from

a file, it exits with a nonzero exit status after printing the stack trace.

(Exceptions handled by an <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> clause in a <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> statement

are not errors in this context.) Some errors are unconditionally fatal and

cause an exit with a nonzero exit; this applies to internal inconsistencies and

some cases of running out of memory. All error messages are written to the

standard error stream; normal output from executed commands is written to

standard output.</p>

<p>Typing the interrupt character (usually <kbd class="kbd docutils literal notranslate">Control-C</kbd> or <kbd class="kbd docutils literal notranslate">Delete</kbd>) to the primary or

secondary prompt cancels the input and returns to the primary prompt. <a class="footnote-reference" href="#id2" id="id1">[1]</a>

Typing an interrupt while a command is executing raises the

<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> exception, which may be handled by a <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>

statement.</p>

</div>

<span id="tut-scripts"></span><h3>16.1.2. Executable Python Scripts<a class="headerlink" href="#executable-python-scripts" title="本標題的永久連結">¶</a></h3>

<p>On BSD’ish Unix systems, Python scripts can be made directly executable, like

shell scripts, by putting the line</p>

<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/env python3.5</span>

</pre></div>

</div>

<p>(assuming that the interpreter is on the user’s <span class="target" id="index-0"></span><code class="xref std std-envvar docutils literal notranslate"><span class="pre">PATH</span></code>) at the beginning

of the script and giving the file an executable mode. The <code class="docutils literal notranslate"><span class="pre">#!</span></code> must be the

first two characters of the file. On some platforms, this first line must end

with a Unix-style line ending (<code class="docutils literal notranslate"><span class="pre">'\n'</span></code>), not a Windows (<code class="docutils literal notranslate"><span class="pre">'\r\n'</span></code>) line

ending. Note that the hash, or pound, character, <code class="docutils literal notranslate"><span class="pre">'#'</span></code>, is used to start a

comment in Python.</p>

<p>The script can be given an executable mode, or permission, using the

<strong class="program">chmod</strong> command.</p>

<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> chmod +x myscript.py

</pre></div>

</div>

<p>On Windows systems, there is no notion of an 「executable mode」. The Python

installer automatically associates <code class="docutils literal notranslate"><span class="pre">.py</span></code> files with <code class="docutils literal notranslate"><span class="pre">python.exe</span></code> so that

a double-click on a Python file will run it as a script. The extension can

also be <code class="docutils literal notranslate"><span class="pre">.pyw</span></code>, in that case, the console window that normally appears is

suppressed.</p>

</div>

<span id="tut-startup"></span><h3>16.1.3. The Interactive Startup File<a class="headerlink" href="#the-interactive-startup-file" title="本標題的永久連結">¶</a></h3>

<p>When you use Python interactively, it is frequently handy to have some standard

commands executed every time the interpreter is started. You can do this by

setting an environment variable named <span class="target" id="index-1"></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> to the name of a

file containing your start-up commands. This is similar to the <code class="file docutils literal notranslate"><span class="pre">.profile</span></code>

feature of the Unix shells.</p>

<p>This file is only read in interactive sessions, not when Python reads commands

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

commands (which otherwise behaves like an interactive session). It is executed

in the same namespace where interactive commands are executed, so that objects

that it defines or imports can be used without qualification in the interactive

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

file.</p>

<p>If you want to read an additional start-up file from the current directory, you

can program this in the global start-up file using code like <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>.

If you want to use the startup file in a script, you must do this explicitly

in the script:</p>

<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">os</span>

<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>

<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>

<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>

<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>

<span class="n">exec</span><span class="p">(</span><span class="n">startup_file</span><span class="p">)</span>

</pre></div>

</div>

<span id="tut-customize"></span><h3>16.1.4. The Customization Modules<a class="headerlink" href="#the-customization-modules" title="本標題的永久連結">¶</a></h3>

<p>Python provides two hooks to let you customize it: <code class="xref py py-mod docutils literal notranslate"><span class="pre">sitecustomize</span></code> and

<code class="xref py py-mod docutils literal notranslate"><span class="pre">usercustomize</span></code>. To see how it works, you need first to find the location

of your user site-packages directory. Start Python and run this code:</p>

<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>

<span class="gp">>>> </span><span class="n">site</span><span class="o">.</span><span class="n">getusersitepackages</span><span class="p">()</span>

<span class="go">'/home/user/.local/lib/python3.5/site-packages'</span>

</pre></div>

</div>

<p>Now you can create a file named <code class="file docutils literal notranslate"><span class="pre">usercustomize.py</span></code> in that directory and

put anything you want in it. It will affect every invocation of Python, unless

it is started with the <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> option to disable the automatic import.</p>

<p><code class="xref py py-mod docutils literal notranslate"><span class="pre">sitecustomize</span></code> works in the same way, but is typically created by an

administrator of the computer in the global site-packages directory, and is

imported before <code class="xref py py-mod docutils literal notranslate"><span class="pre">usercustomize</span></code>. See the documentation of the <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>

module for more details.</p>

<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>A problem with the GNU Readline package may prevent this.</td></tr>

</tbody>

</table>

</div>

<ul>

<li><a class="reference internal" href="#error-handling">16.1.1. Error Handling</a></li>

<li><a class="reference internal" href="#executable-python-scripts">16.1.2. Executable Python Scripts</a></li>

<li><a class="reference internal" href="#the-interactive-startup-file">16.1.3. The Interactive Startup File</a></li>

<li><a class="reference internal" href="#the-customization-modules">16.1.4. The Customization Modules</a></li>

</ul>

</li>

</ul>

</li>

</ul>

<p class="topless"><a href="floatingpoint.html"

title="上一章">15. Floating Point Arithmetic: Issues and Limitations</a></p>

<p class="topless"><a href="../using/index.html"

title="下一章">Python Setup and Usage</a></p>

<li><a href="../bugs.html">Report a Bug</a></li>

<li>

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