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  <div class="section" id="not-using-dict-comprehensions">
<h1>Not using dict comprehensions<a class="headerlink" href="#not-using-dict-comprehensions" title="Permalink to this headline">¶</a></h1>
<p>You may encounter the old style of initializing a dict (passing an iterable of key-value pairs) in older Python code written before version 2.7. The new dict comprehension style is functionally equivalent and is much more readable. Consider refactoring the old-style code to use the new style (but only if you are using Python 2.7 or higher).</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 demonstrates the old syntax of dict initialization. Although there is nothing syntactically wrong with this code, it is somewhat hard to read.</p>
<div class="code python highlight-default"><div class="highlight"><pre><span></span><span class="n">numbers</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"># hard to read</span>
<span class="n">my_dict</span> <span class="o">=</span> <span class="nb">dict</span><span class="p">([(</span><span class="n">number</span><span class="p">,</span><span class="n">number</span><span class="o">*</span><span class="mi">2</span><span class="p">)</span> <span class="k">for</span> <span class="n">number</span> <span class="ow">in</span> <span class="n">numbers</span><span class="p">])</span>

<span class="nb">print</span><span class="p">(</span><span class="n">my_dict</span><span class="p">)</span>  <span class="c1"># {1: 2, 2: 4, 3: 6}</span>
</pre></div>
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<div class="section" id="best-practice">
<h2>Best practice<a class="headerlink" href="#best-practice" title="Permalink to this headline">¶</a></h2>
<p>The modified code below uses the new dict comprehension syntax which was introduced in Python 2.7.</p>
<div class="code python highlight-default"><div class="highlight"><pre><span></span><span class="n">numbers</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="n">my_dict</span> <span class="o">=</span> <span class="p">{</span><span class="n">number</span><span class="p">:</span> <span class="n">number</span> <span class="o">*</span> <span class="mi">2</span> <span class="k">for</span> <span class="n">number</span> <span class="ow">in</span> <span class="n">numbers</span><span class="p">}</span>

<span class="nb">print</span><span class="p">(</span><span class="n">my_dict</span><span class="p">)</span>  <span class="c1"># {1: 2, 2: 4, 3: 6}</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><a class="reference external" href="http://stackoverflow.com/questions/1747817/python-create-a-dictionary-with-list-comprehension">Stack Overflow - Create a dictionary with list comprehesion</a></li>
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