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  <div class="section" id="comparing-things-to-none-the-wrong-way">
<h1>Comparing things to <cite>None</cite> the wrong way<a class="headerlink" href="#comparing-things-to-none-the-wrong-way" title="Permalink to this headline">¶</a></h1>
<p>Per the PEP 8 Style Guide, the preferred way to compare something to <code class="docutils literal"><span class="pre">None</span></code> is the pattern <code class="docutils literal"><span class="pre">if</span> <span class="pre">Cond</span> <span class="pre">is</span> <span class="pre">None</span></code>. This is only a guideline. It can be ignored if needed. But the purpose of the PEP 8 style guidelines is to improve the readability of code.</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 statement below uses the equality operator to compare a variable to <code class="docutils literal"><span class="pre">None</span></code>. This is not the PEP 8 preferred approach to comparing values to <code class="docutils literal"><span class="pre">None</span></code>.</p>
<div class="code python highlight-default"><div class="highlight"><pre><span></span><span class="n">number</span> <span class="o">=</span> <span class="kc">None</span>

<span class="k">if</span> <span class="n">number</span> <span class="o">==</span> <span class="kc">None</span><span class="p">:</span>
    <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;This works, but is not the preferred PEP 8 pattern&quot;</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="best-practice">
<h2>Best practice<a class="headerlink" href="#best-practice" title="Permalink to this headline">¶</a></h2>
<div class="section" id="compare-values-to-none-using-the-pattern-if-cond-is-none">
<h3>Compare values to <code class="docutils literal"><span class="pre">None</span></code> using the pattern <code class="docutils literal"><span class="pre">if</span> <span class="pre">cond</span> <span class="pre">is</span> <span class="pre">None</span></code><a class="headerlink" href="#compare-values-to-none-using-the-pattern-if-cond-is-none" title="Permalink to this headline">¶</a></h3>
<p>The code below uses the PEP 8 preferred pattern of <code class="docutils literal"><span class="pre">if</span> <span class="pre">cond</span> <span class="pre">is</span> <span class="pre">None</span></code>.</p>
<div class="code python highlight-default"><div class="highlight"><pre><span></span><span class="n">number</span> <span class="o">=</span> <span class="kc">None</span>

<span class="k">if</span> <span class="n">number</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
    <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;PEP 8 Style Guide prefers this pattern&quot;</span><span class="p">)</span>
</pre></div>
</div>
<p>Here the identity operator <code class="docutils literal"><span class="pre">is</span></code> is used. It will check whether <code class="docutils literal"><span class="pre">number</span></code> is identical to <code class="docutils literal"><span class="pre">None</span></code>.
<code class="docutils literal"><span class="pre">is</span></code> will return to <code class="docutils literal"><span class="pre">True</span></code> only if the two variables point to the same object.</p>
</div>
</div>
<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://legacy.python.org/dev/peps/pep-0008/#programming-recommendations">PEP 8 Style Guide - Programming Recommendations</a></li>
<li><a class="reference external" href="http://stackoverflow.com/questions/1504717/why-does-comparing-strings-in-python-using-either-or-is-sometimes-produce">stackoverflow</a></li>
</ul>
</div>
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