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<div class="section" id="using-an-unpythonic-loop">
<h1>Using an unpythonic loop<a class="headerlink" href="#using-an-unpythonic-loop" title="Permalink to this headline">¶</a></h1>
<p><a class="reference external" href="http://legacy.python.org/dev/peps/pep-0020/">PEP 20</a> states “There should be one– and preferably only one –obvious way to do it.” Creating a loop that uses an incrementing index to access each element of a list within the loop construct is not the preferred style for accessing each element in a list. The preferred style is to use <code class="docutils literal notranslate"><span class="pre">enumerate()</span></code> to simultaneously retrieve the index and list element.</p>
<div class="section" id="anti-pattern">
<h2>Anti-pattern<a class="headerlink" href="#anti-pattern" title="Permalink to this headline">¶</a></h2>
<p>The code below uses an index variable <code class="docutils literal notranslate"><span class="pre">i</span></code> in a <code class="docutils literal notranslate"><span class="pre">for</span></code> loop to iterate through the elements of a list. This is not the preferred style for iterating through a list in Python.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="n">l</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">]</span>
<span class="c1"># creating index variable</span>
<span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="nb">len</span><span class="p">(</span><span class="n">l</span><span class="p">)):</span>
<span class="c1"># using index to access list</span>
<span class="n">le</span> <span class="o">=</span> <span class="n">l</span><span class="p">[</span><span class="n">i</span><span class="p">]</span>
<span class="nb">print</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="n">le</span><span class="p">)</span>
</pre></div>
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<h2>Best practice<a class="headerlink" href="#best-practice" title="Permalink to this headline">¶</a></h2>
<div class="section" id="retrieve-index-and-element-when-defining-loop">
<h3>Retrieve index and element when defining loop<a class="headerlink" href="#retrieve-index-and-element-when-defining-loop" title="Permalink to this headline">¶</a></h3>
<p>The updated code below demonstrates the Pythonic style for iterating through a list. When you define two variables in a <code class="docutils literal notranslate"><span class="pre">for</span></code> loop in conjunction with a call to <code class="docutils literal notranslate"><span class="pre">enumerate()</span></code> on a list, Python automatically assigns the first variable as an index variable, and the second variable as the corresponding list element value for that index location in the list.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">le</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">(</span><span class="n">l</span><span class="p">):</span>
<span class="nb">print</span><span class="p">(</span><span class="n">i</span><span class="p">,</span> <span class="n">le</span><span class="p">)</span>
</pre></div>
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<div class="section" id="references">
<h2>References<a class="headerlink" href="#references" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li><p><a class="reference external" href="http://legacy.python.org/dev/peps/pep-0020/">PEP 20 - The Zen of Python</a></p></li>
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