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<div class="section" id="brief-tour-of-the-standard-library">
<span id="tut-brieftour"></span><h1>10. Python 標準函式庫概覽<a class="headerlink" href="#brief-tour-of-the-standard-library" title="本標題的永久連結">¶</a></h1>
<div class="section" id="operating-system-interface">
<span id="tut-os-interface"></span><h2>10.1. 作業系統介面<a class="headerlink" href="#operating-system-interface" title="本標題的永久連結">¶</a></h2>
<p><a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate"><span class="pre">os</span></code></a> 模組提供了數十個與作業系統溝通的函式：</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">os</span>
<span class="gp">>>> </span><span class="n">os</span><span class="o">.</span><span class="n">getcwd</span><span class="p">()</span> <span class="c1"># Return the current working directory</span>
<span class="go">'C:\\Python37'</span>
<span class="gp">>>> </span><span class="n">os</span><span class="o">.</span><span class="n">chdir</span><span class="p">(</span><span class="s1">'/server/accesslogs'</span><span class="p">)</span> <span class="c1"># Change current working directory</span>
<span class="gp">>>> </span><span class="n">os</span><span class="o">.</span><span class="n">system</span><span class="p">(</span><span class="s1">'mkdir today'</span><span class="p">)</span> <span class="c1"># Run the command mkdir in the system shell</span>
<span class="go">0</span>
</pre></div>
</div>
<p>務必使用 <code class="docutils literal notranslate"><span class="pre">import</span> <span class="pre">os</span></code> 而非 <code class="docutils literal notranslate"><span class="pre">from</span> <span class="pre">os</span> <span class="pre">import</span> <span class="pre">*</span></code>。這將避免因系統不同而實作有差異的 <a class="reference internal" href="../library/os.html#os.open" title="os.open"><code class="xref py py-func docutils literal notranslate"><span class="pre">os.open()</span></code></a> 覆蓋內建函式 <a class="reference internal" href="../library/functions.html#open" title="open"><code class="xref py py-func docutils literal notranslate"><span class="pre">open()</span></code></a>。</p>
<p id="index-0">在使用 <a class="reference internal" href="../library/os.html#module-os" title="os: Miscellaneous operating system interfaces."><code class="xref py py-mod docutils literal notranslate"><span class="pre">os</span></code></a> 諸如此類大型模組時搭配內建函式 <a class="reference internal" href="../library/functions.html#dir" title="dir"><code class="xref py py-func docutils literal notranslate"><span class="pre">dir()</span></code></a> 和 <a class="reference internal" href="../library/functions.html#help" title="help"><code class="xref py py-func docutils literal notranslate"><span class="pre">help()</span></code></a> 是非常有用的:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">os</span>
<span class="gp">>>> </span><span class="nb">dir</span><span class="p">(</span><span class="n">os</span><span class="p">)</span>
<span class="go"><returns a list of all module functions></span>
<span class="gp">>>> </span><span class="n">help</span><span class="p">(</span><span class="n">os</span><span class="p">)</span>
<span class="go"><returns an extensive manual page created from the module's docstrings></span>
</pre></div>
</div>
<p>對於日常檔案和目錄管理任務， <a class="reference internal" href="../library/shutil.html#module-shutil" title="shutil: High-level file operations, including copying."><code class="xref py py-mod docutils literal notranslate"><span class="pre">shutil</span></code></a> 模組提供了更容易使用的高階介面：</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">shutil</span>
<span class="gp">>>> </span><span class="n">shutil</span><span class="o">.</span><span class="n">copyfile</span><span class="p">(</span><span class="s1">'data.db'</span><span class="p">,</span> <span class="s1">'archive.db'</span><span class="p">)</span>
<span class="go">'archive.db'</span>
<span class="gp">>>> </span><span class="n">shutil</span><span class="o">.</span><span class="n">move</span><span class="p">(</span><span class="s1">'/build/executables'</span><span class="p">,</span> <span class="s1">'installdir'</span><span class="p">)</span>
<span class="go">'installdir'</span>
</pre></div>
</div>
</div>
<div class="section" id="file-wildcards">
<span id="tut-file-wildcards"></span><h2>10.2. 檔案之萬用字元<a class="headerlink" href="#file-wildcards" title="本標題的永久連結">¶</a></h2>
<p>The <a class="reference internal" href="../library/glob.html#module-glob" title="glob: Unix shell style pathname pattern expansion."><code class="xref py py-mod docutils literal notranslate"><span class="pre">glob</span></code></a> module provides a function for making file lists from directory
wildcard searches:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">glob</span>
<span class="gp">>>> </span><span class="n">glob</span><span class="o">.</span><span class="n">glob</span><span class="p">(</span><span class="s1">'*.py'</span><span class="p">)</span>
<span class="go">['primes.py', 'random.py', 'quote.py']</span>
</pre></div>
</div>
</div>
<div class="section" id="command-line-arguments">
<span id="tut-command-line-arguments"></span><h2>10.3. 命令列引數<a class="headerlink" href="#command-line-arguments" title="本標題的永久連結">¶</a></h2>
<p>通用工具腳本常需要處理命令列引數。這些引數會以串列形式存放在 <a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> 模組的 <em>argv</em> 此變數中。例如在命令列執行 <code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">demo.py</span> <span class="pre">one</span> <span class="pre">two</span> <span class="pre">three</span></code> 會有以下輸出結果:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">sys</span>
<span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">)</span>
<span class="go">['demo.py', 'one', 'two', 'three']</span>
</pre></div>
</div>
<p><a class="reference internal" href="../library/getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-mod docutils literal notranslate"><span class="pre">getopt</span></code></a> 模組使用Unix <a class="reference internal" href="../library/getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-func docutils literal notranslate"><span class="pre">getopt()</span></code></a> 函式來處理 <em>sys.argv</em>。更強大且具有彈性的命令列處理可由 <a class="reference internal" href="../library/argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> 模組提供。</p>
</div>
<div class="section" id="error-output-redirection-and-program-termination">
<span id="tut-stderr"></span><h2>10.4. 錯誤輸出重新導向與程式終止<a class="headerlink" href="#error-output-redirection-and-program-termination" title="本標題的永久連結">¶</a></h2>
<p><a class="reference internal" href="../library/sys.html#module-sys" title="sys: Access system-specific parameters and functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">sys</span></code></a> 模組也有 <em>stdin</em>，<em>stdout</em>，和 <em>stderr</em> 等變數。即使當 <em>stdout</em> 被重新導向時，後者 <em>stderr</em> 可輸出發送警告和錯誤訊息。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">'Warning, log file not found starting a new one</span><span class="se">\n</span><span class="s1">'</span><span class="p">)</span>
<span class="go">Warning, log file not found starting a new one</span>
</pre></div>
</div>
<p>終止腳本最直接的方式就是利用 <code class="docutils literal notranslate"><span class="pre">sys.exit()</span></code>。</p>
</div>
<div class="section" id="string-pattern-matching">
<span id="tut-string-pattern-matching"></span><h2>10.5. 字串樣式比對<a class="headerlink" href="#string-pattern-matching" title="本標題的永久連結">¶</a></h2>
<p><a class="reference internal" href="../library/re.html#module-re" title="re: Regular expression operations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">re</span></code></a> 模組提供正規表示式 (regular expression) 做進階的字串處理。當要處理複雜的比對以及操作時，正規表示式是簡潔且經過最佳化的解決方案。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">re</span>
<span class="gp">>>> </span><span class="n">re</span><span class="o">.</span><span class="n">findall</span><span class="p">(</span><span class="sa">r</span><span class="s1">'\bf[a-z]*'</span><span class="p">,</span> <span class="s1">'which foot or hand fell fastest'</span><span class="p">)</span>
<span class="go">['foot', 'fell', 'fastest']</span>
<span class="gp">>>> </span><span class="n">re</span><span class="o">.</span><span class="n">sub</span><span class="p">(</span><span class="sa">r</span><span class="s1">'(\b[a-z]+) \1'</span><span class="p">,</span> <span class="sa">r</span><span class="s1">'\1'</span><span class="p">,</span> <span class="s1">'cat in the the hat'</span><span class="p">)</span>
<span class="go">'cat in the hat'</span>
</pre></div>
</div>
<p>當只需要簡單的字串操作時，因為可讀性以及方便除錯，字串本身的方法是比較建議的。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="s1">'tea for too'</span><span class="o">.</span><span class="n">replace</span><span class="p">(</span><span class="s1">'too'</span><span class="p">,</span> <span class="s1">'two'</span><span class="p">)</span>
<span class="go">'tea for two'</span>
</pre></div>
</div>
</div>
<div class="section" id="mathematics">
<span id="tut-mathematics"></span><h2>10.6. 數學相關<a class="headerlink" href="#mathematics" title="本標題的永久連結">¶</a></h2>
<p><a class="reference internal" href="../library/math.html#module-math" title="math: Mathematical functions (sin() etc.)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">math</span></code></a> 模組提供了 C 函式庫中底層的浮點數運算的函式。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">math</span>
<span class="gp">>>> </span><span class="n">math</span><span class="o">.</span><span class="n">cos</span><span class="p">(</span><span class="n">math</span><span class="o">.</span><span class="n">pi</span> <span class="o">/</span> <span class="mi">4</span><span class="p">)</span>
<span class="go">0.70710678118654757</span>
<span class="gp">>>> </span><span class="n">math</span><span class="o">.</span><span class="n">log</span><span class="p">(</span><span class="mi">1024</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
<span class="go">10.0</span>
</pre></div>
</div>
<p><a class="reference internal" href="../library/random.html#module-random" title="random: Generate pseudo-random numbers with various common distributions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">random</span></code></a> 模組提供了隨機選擇的工具。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">random</span>
<span class="gp">>>> </span><span class="n">random</span><span class="o">.</span><span class="n">choice</span><span class="p">([</span><span class="s1">'apple'</span><span class="p">,</span> <span class="s1">'pear'</span><span class="p">,</span> <span class="s1">'banana'</span><span class="p">])</span>
<span class="go">'apple'</span>
<span class="gp">>>> </span><span class="n">random</span><span class="o">.</span><span class="n">sample</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span> <span class="mi">10</span><span class="p">)</span> <span class="c1"># sampling without replacement</span>
<span class="go">[30, 83, 16, 4, 8, 81, 41, 50, 18, 33]</span>
<span class="gp">>>> </span><span class="n">random</span><span class="o">.</span><span class="n">random</span><span class="p">()</span> <span class="c1"># random float</span>
<span class="go">0.17970987693706186</span>
<span class="gp">>>> </span><span class="n">random</span><span class="o">.</span><span class="n">randrange</span><span class="p">(</span><span class="mi">6</span><span class="p">)</span> <span class="c1"># random integer chosen from range(6)</span>
<span class="go">4</span>
</pre></div>
</div>
<p><a class="reference internal" href="../library/statistics.html#module-statistics" title="statistics: mathematical statistics functions"><code class="xref py py-mod docutils literal notranslate"><span class="pre">statistics</span></code></a> 模組提供了替數值資料計算基本統計量（包括平均、中位數、變異量數等）的功能。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">statistics</span>
<span class="gp">>>> </span><span class="n">data</span> <span class="o">=</span> <span class="p">[</span><span class="mf">2.75</span><span class="p">,</span> <span class="mf">1.75</span><span class="p">,</span> <span class="mf">1.25</span><span class="p">,</span> <span class="mf">0.25</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">,</span> <span class="mf">1.25</span><span class="p">,</span> <span class="mf">3.5</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">statistics</span><span class="o">.</span><span class="n">mean</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="go">1.6071428571428572</span>
<span class="gp">>>> </span><span class="n">statistics</span><span class="o">.</span><span class="n">median</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="go">1.25</span>
<span class="gp">>>> </span><span class="n">statistics</span><span class="o">.</span><span class="n">variance</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="go">1.3720238095238095</span>
</pre></div>
</div>
<p>Scipy 專案 <<a class="reference external" href="https://scipy.org">https://scipy.org</a>> 上也有許多數值計算相關的模組。</p>
</div>
<div class="section" id="internet-access">
<span id="tut-internet-access"></span><h2>10.7. 網路存取<a class="headerlink" href="#internet-access" title="本標題的永久連結">¶</a></h2>
<p>Python 中有許多存取網路以及處理網路協定。最簡單的兩個例子包括 <a class="reference internal" href="../library/urllib.request.html#module-urllib.request" title="urllib.request: Extensible library for opening URLs."><code class="xref py py-mod docutils literal notranslate"><span class="pre">urllib.request</span></code></a> 模組可以從網址抓取資料以及 <a class="reference internal" href="../library/smtplib.html#module-smtplib" title="smtplib: SMTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">smtplib</span></code></a> 可以用來寄郵件。:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">urllib.request</span> <span class="k">import</span> <span class="n">urlopen</span>
<span class="gp">>>> </span><span class="k">with</span> <span class="n">urlopen</span><span class="p">(</span><span class="s1">'http://tycho.usno.navy.mil/cgi-bin/timer.pl'</span><span class="p">)</span> <span class="k">as</span> <span class="n">response</span><span class="p">:</span>
<span class="gp">... </span> <span class="k">for</span> <span class="n">line</span> <span class="ow">in</span> <span class="n">response</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">line</span> <span class="o">=</span> <span class="n">line</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s1">'utf-8'</span><span class="p">)</span> <span class="c1"># Decoding the binary data to text.</span>
<span class="gp">... </span> <span class="k">if</span> <span class="s1">'EST'</span> <span class="ow">in</span> <span class="n">line</span> <span class="ow">or</span> <span class="s1">'EDT'</span> <span class="ow">in</span> <span class="n">line</span><span class="p">:</span> <span class="c1"># look for Eastern Time</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">line</span><span class="p">)</span>
<span class="go"><BR>Nov. 25, 09:43:32 PM EST</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">smtplib</span>
<span class="gp">>>> </span><span class="n">server</span> <span class="o">=</span> <span class="n">smtplib</span><span class="o">.</span><span class="n">SMTP</span><span class="p">(</span><span class="s1">'localhost'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">server</span><span class="o">.</span><span class="n">sendmail</span><span class="p">(</span><span class="s1">'soothsayer@example.org'</span><span class="p">,</span> <span class="s1">'jcaesar@example.org'</span><span class="p">,</span>
<span class="gp">... </span><span class="sd">"""To: jcaesar@example.org</span>
<span class="gp">... </span><span class="sd">From: soothsayer@example.org</span>
<span class="gp">...</span><span class="sd"></span>
<span class="gp">... </span><span class="sd">Beware the Ides of March.</span>
<span class="gp">... </span><span class="sd">"""</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">server</span><span class="o">.</span><span class="n">quit</span><span class="p">()</span>
</pre></div>
</div>
<p>（注意第二個例子中需要在本地端執行一個郵件伺服器）</p>
</div>
<div class="section" id="dates-and-times">
<span id="tut-dates-and-times"></span><h2>10.8. 日期與時間<a class="headerlink" href="#dates-and-times" title="本標題的永久連結">¶</a></h2>
<p><a class="reference internal" href="../library/datetime.html#module-datetime" title="datetime: Basic date and time types."><code class="xref py py-mod docutils literal notranslate"><span class="pre">datetime</span></code></a> 模組中有許多類別供以操作日期以及時間，從簡單從複雜都有。模組支援日期與時間的運算，而實作的重點是有效率的成員擷取以達到輸出格式化以及操作。模組也提供支援時區換算的類別。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># dates are easily constructed and formatted</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">datetime</span> <span class="k">import</span> <span class="n">date</span>
<span class="gp">>>> </span><span class="n">now</span> <span class="o">=</span> <span class="n">date</span><span class="o">.</span><span class="n">today</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">now</span>
<span class="go">datetime.date(2003, 12, 2)</span>
<span class="gp">>>> </span><span class="n">now</span><span class="o">.</span><span class="n">strftime</span><span class="p">(</span><span class="s2">"%m-</span><span class="si">%d</span><span class="s2">-%y. </span><span class="si">%d</span><span class="s2"> %b %Y is a %A on the </span><span class="si">%d</span><span class="s2"> day of %B."</span><span class="p">)</span>
<span class="go">'12-02-03. 02 Dec 2003 is a Tuesday on the 02 day of December.'</span>
<span class="gp">>>> </span><span class="c1"># dates support calendar arithmetic</span>
<span class="gp">>>> </span><span class="n">birthday</span> <span class="o">=</span> <span class="n">date</span><span class="p">(</span><span class="mi">1964</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">31</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">age</span> <span class="o">=</span> <span class="n">now</span> <span class="o">-</span> <span class="n">birthday</span>
<span class="gp">>>> </span><span class="n">age</span><span class="o">.</span><span class="n">days</span>
<span class="go">14368</span>
</pre></div>
</div>
</div>
<div class="section" id="data-compression">
<span id="tut-data-compression"></span><h2>10.9. 資料壓縮<a class="headerlink" href="#data-compression" title="本標題的永久連結">¶</a></h2>
<p>常見的解壓縮以及壓縮格式都有直接支援。 包括： <a class="reference internal" href="../library/zlib.html#module-zlib" title="zlib: Low-level interface to compression and decompression routines compatible with gzip."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zlib</span></code></a> ， <a class="reference internal" href="../library/gzip.html#module-gzip" title="gzip: Interfaces for gzip compression and decompression using file objects."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gzip</span></code></a> ， <a class="reference internal" href="../library/bz2.html#module-bz2" title="bz2: Interfaces for bzip2 compression and decompression."><code class="xref py py-mod docutils literal notranslate"><span class="pre">bz2</span></code></a>， <a class="reference internal" href="../library/lzma.html#module-lzma" title="lzma: A Python wrapper for the liblzma compression library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">lzma</span></code></a> ，<a class="reference internal" href="../library/zipfile.html#module-zipfile" title="zipfile: Read and write ZIP-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">zipfile</span></code></a> 以及 <a class="reference internal" href="../library/tarfile.html#module-tarfile" title="tarfile: Read and write tar-format archive files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">tarfile</span></code></a> 。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">zlib</span>
<span class="gp">>>> </span><span class="n">s</span> <span class="o">=</span> <span class="sa">b</span><span class="s1">'witch which has which witches wrist watch'</span>
<span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">s</span><span class="p">)</span>
<span class="go">41</span>
<span class="gp">>>> </span><span class="n">t</span> <span class="o">=</span> <span class="n">zlib</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="n">s</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>
<span class="go">37</span>
<span class="gp">>>> </span><span class="n">zlib</span><span class="o">.</span><span class="n">decompress</span><span class="p">(</span><span class="n">t</span><span class="p">)</span>
<span class="go">b'witch which has which witches wrist watch'</span>
<span class="gp">>>> </span><span class="n">zlib</span><span class="o">.</span><span class="n">crc32</span><span class="p">(</span><span class="n">s</span><span class="p">)</span>
<span class="go">226805979</span>
</pre></div>
</div>
</div>
<div class="section" id="performance-measurement">
<span id="tut-performance-measurement"></span><h2>10.10. 效能量測<a class="headerlink" href="#performance-measurement" title="本標題的永久連結">¶</a></h2>
<p>有一些 Python 使用者很想了解同個問題的不同實作方法的效能差異。 Python 提供評估了效能差異的工具。</p>
<p>舉例來說， 有人可能會試著用 tuple 的打包機制來交換引數代替傳統的方式。 <a class="reference internal" href="../library/timeit.html#module-timeit" title="timeit: Measure the execution time of small code snippets."><code class="xref py py-mod docutils literal notranslate"><span class="pre">timeit</span></code></a> 模組可以迅速地展示效能的進步。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">timeit</span> <span class="k">import</span> <span class="n">Timer</span>
<span class="gp">>>> </span><span class="n">Timer</span><span class="p">(</span><span class="s1">'t=a; a=b; b=t'</span><span class="p">,</span> <span class="s1">'a=1; b=2'</span><span class="p">)</span><span class="o">.</span><span class="n">timeit</span><span class="p">()</span>
<span class="go">0.57535828626024577</span>
<span class="gp">>>> </span><span class="n">Timer</span><span class="p">(</span><span class="s1">'a,b = b,a'</span><span class="p">,</span> <span class="s1">'a=1; b=2'</span><span class="p">)</span><span class="o">.</span><span class="n">timeit</span><span class="p">()</span>
<span class="go">0.54962537085770791</span>
</pre></div>
</div>
<p>相對於 <a class="reference internal" href="../library/timeit.html#module-timeit" title="timeit: Measure the execution time of small code snippets."><code class="xref py py-mod docutils literal notranslate"><span class="pre">timeit</span></code></a> 模組提供這麼細的粒度，<a class="reference internal" href="../library/profile.html#module-profile" title="profile: Python source profiler."><code class="xref py py-mod docutils literal notranslate"><span class="pre">profile</span></code></a> 模組以及 <a class="reference internal" href="../library/profile.html#module-pstats" title="pstats: Statistics object for use with the profiler."><code class="xref py py-mod docutils literal notranslate"><span class="pre">pstats</span></code></a> 模組則提供了一些在大型的程式碼識別關鍵臨界區間（Critical Section）的工具。</p>
</div>
<div class="section" id="quality-control">
<span id="tut-quality-control"></span><h2>10.11. 品質控管<a class="headerlink" href="#quality-control" title="本標題的永久連結">¶</a></h2>
<p>達到高品質軟體的一個方法當開發時對每個函式寫測試以及在開發過程中要不斷的跑這些測試。</p>
<p><a class="reference internal" href="../library/doctest.html#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate"><span class="pre">doctest</span></code></a> 模組提供了一個工具， 掃描模組並根據程式中內嵌的文件字符串執行測試。測試構造如同簡單的將它的輸出結果剪下並貼上到文件字符串中。 通過用戶提供的例子， 它強化了文件， 允許 doctest 模塊組認代碼的結果是否與文件一致:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">average</span><span class="p">(</span><span class="n">values</span><span class="p">):</span>
<span class="sd">"""Computes the arithmetic mean of a list of numbers.</span>
<span class="sd"> >>> print(average([20, 30, 70]))</span>
<span class="sd"> 40.0</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="nb">sum</span><span class="p">(</span><span class="n">values</span><span class="p">)</span> <span class="o">/</span> <span class="nb">len</span><span class="p">(</span><span class="n">values</span><span class="p">)</span>
<span class="kn">import</span> <span class="nn">doctest</span>
<span class="n">doctest</span><span class="o">.</span><span class="n">testmod</span><span class="p">()</span> <span class="c1"># automatically validate the embedded tests</span>
</pre></div>
</div>
<p><a class="reference internal" href="../library/unittest.html#module-unittest" title="unittest: Unit testing framework for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">unittest</span></code></a> 模組不像 <a class="reference internal" href="../library/doctest.html#module-doctest" title="doctest: Test pieces of code within docstrings."><code class="xref py py-mod docutils literal notranslate"><span class="pre">doctest</span></code></a> 模組這般容易， 但是它提供了更完整的測試集並且可以整合在不同的檔案間。</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">unittest</span>
<span class="k">class</span> <span class="nc">TestStatisticalFunctions</span><span class="p">(</span><span class="n">unittest</span><span class="o">.</span><span class="n">TestCase</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">test_average</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">assertEqual</span><span class="p">(</span><span class="n">average</span><span class="p">([</span><span class="mi">20</span><span class="p">,</span> <span class="mi">30</span><span class="p">,</span> <span class="mi">70</span><span class="p">]),</span> <span class="mf">40.0</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">assertEqual</span><span class="p">(</span><span class="nb">round</span><span class="p">(</span><span class="n">average</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">7</span><span class="p">]),</span> <span class="mi">1</span><span class="p">),</span> <span class="mf">4.3</span><span class="p">)</span>
<span class="k">with</span> <span class="bp">self</span><span class="o">.</span><span class="n">assertRaises</span><span class="p">(</span><span class="ne">ZeroDivisionError</span><span class="p">):</span>
<span class="n">average</span><span class="p">([])</span>
<span class="k">with</span> <span class="bp">self</span><span class="o">.</span><span class="n">assertRaises</span><span class="p">(</span><span class="ne">TypeError</span><span class="p">):</span>
<span class="n">average</span><span class="p">(</span><span class="mi">20</span><span class="p">,</span> <span class="mi">30</span><span class="p">,</span> <span class="mi">70</span><span class="p">)</span>
<span class="n">unittest</span><span class="o">.</span><span class="n">main</span><span class="p">()</span> <span class="c1"># Calling from the command line invokes all tests</span>
</pre></div>
</div>
</div>
<div class="section" id="batteries-included">
<span id="tut-batteries-included"></span><h2>10.12. 標準模組庫<a class="headerlink" href="#batteries-included" title="本標題的永久連結">¶</a></h2>
<p>「batteries included」 是 Python設計哲學。 它的好處是可以透過這些套件使用複雜與強大的功能。 例如:</p>
<ul class="simple">
<li>使用 <a class="reference internal" href="../library/xmlrpc.client.html#module-xmlrpc.client" title="xmlrpc.client: XML-RPC client access."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xmlrpc.client</span></code></a> 和 <a class="reference internal" href="../library/xmlrpc.server.html#module-xmlrpc.server" title="xmlrpc.server: Basic XML-RPC server implementations."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xmlrpc.server</span></code></a> 模組實現遠端控制看似變更為容易。 使用前也不需要先了解相關知識或是掌握 XML 的技能就能直接透過名稱使用模組。</li>
<li>The <a class="reference internal" href="../library/email.html#module-email" title="email: Package supporting the parsing, manipulating, and generating email messages."><code class="xref py py-mod docutils literal notranslate"><span class="pre">email</span></code></a> package is a library for managing email messages, including
MIME and other <span class="target" id="index-1"></span><a class="rfc reference external" href="https://tools.ietf.org/html/rfc2822.html"><strong>RFC 2822</strong></a>-based message documents. Unlike <a class="reference internal" href="../library/smtplib.html#module-smtplib" title="smtplib: SMTP protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">smtplib</span></code></a> and
<a class="reference internal" href="../library/poplib.html#module-poplib" title="poplib: POP3 protocol client (requires sockets)."><code class="xref py py-mod docutils literal notranslate"><span class="pre">poplib</span></code></a> which actually send and receive messages, the email package has
a complete toolset for building or decoding complex message structures
(including attachments) and for implementing internet encoding and header
protocols.</li>
<li>函式庫 <a class="reference internal" href="../library/json.html#module-json" title="json: Encode and decode the JSON format."><code class="xref py py-mod docutils literal notranslate"><span class="pre">json</span></code></a> 套件提供 JSON 資料解析強大的交換格式。 <a class="reference internal" href="../library/csv.html#module-csv" title="csv: Write and read tabular data to and from delimited files."><code class="xref py py-mod docutils literal notranslate"><span class="pre">csv</span></code></a> 模組則提供直接讀寫以逗號分隔值的檔案格式，支援一般資料庫與電子表格。 <a class="reference internal" href="../library/xml.etree.elementtree.html#module-xml.etree.ElementTree" title="xml.etree.ElementTree: Implementation of the ElementTree API."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.etree.ElementTree</span></code></a> ， <a class="reference internal" href="../library/xml.dom.html#module-xml.dom" title="xml.dom: Document Object Model API for Python."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.dom</span></code></a> 與 <a class="reference internal" href="../library/xml.sax.html#module-xml.sax" title="xml.sax: Package containing SAX2 base classes and convenience functions."><code class="xref py py-mod docutils literal notranslate"><span class="pre">xml.sax</span></code></a> 套件則支援 XML 流程。 綜觀所有， 這些模組和套件都簡化了 Python 應用程式與其他工具之間的資料交換。</li>
<li><code class="xref py py-mod docutils literal notranslate"><span class="pre">sqllite3</span></code> 套件作為包覆 SQLite 資料庫的函式庫， 提供一個一致性的資料庫用來更新與操作使用些微非標準的 SQL 語法。</li>
<li>有數種支援國際化模組 <a class="reference internal" href="../library/gettext.html#module-gettext" title="gettext: Multilingual internationalization services."><code class="xref py py-mod docutils literal notranslate"><span class="pre">gettext</span></code></a>，<a class="reference internal" href="../library/locale.html#module-locale" title="locale: Internationalization services."><code class="xref py py-mod docutils literal notranslate"><span class="pre">locale</span></code></a>，和 <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> 等套件。</li>
</ul>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar" role="navigation" aria-label="main navigation">
<div class="sphinxsidebarwrapper">
<h3><a href="../contents.html">目錄</a></h3>
<ul>
<li><a class="reference internal" href="#">10. Python 標準函式庫概覽</a><ul>
<li><a class="reference internal" href="#operating-system-interface">10.1. 作業系統介面</a></li>
<li><a class="reference internal" href="#file-wildcards">10.2. 檔案之萬用字元</a></li>
<li><a class="reference internal" href="#command-line-arguments">10.3. 命令列引數</a></li>
<li><a class="reference internal" href="#error-output-redirection-and-program-termination">10.4. 錯誤輸出重新導向與程式終止</a></li>
<li><a class="reference internal" href="#string-pattern-matching">10.5. 字串樣式比對</a></li>
<li><a class="reference internal" href="#mathematics">10.6. 數學相關</a></li>
<li><a class="reference internal" href="#internet-access">10.7. 網路存取</a></li>
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