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<div class="section" id="class-method-and-static-method">
<h1>Class method and static method<a class="headerlink" href="#class-method-and-static-method" title="Permalink to this headline">¶</a></h1>
<p>A class method is a method bound to a class and not to an instance.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">MyFantasticClass</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">interrupt</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">'Or a woman !'</span>
<span class="gp">>>> </span><span class="n">m</span> <span class="o">=</span> <span class="n">MyFantasticClass</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">m</span><span class="o">.</span><span class="n">interrupt</span><span class="p">()</span>
<span class="go">Or a woman !</span>
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<p>The <em>interrupt</em> function is an instance function, it receives self as an
argument. This is not adapted here, because for the function to be
used, an instance must be created: even though the <em>interrupt</em> method does
not make use of the instance, it is passed as an input parameter to
the function.</p>
<p><strong>How to define the *interrupt* method so that it is called directly on
the class without having to create an instance?</strong></p>
<p>Example :</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">MyFantasticClass</span><span class="o">.</span><span class="n">interrupt</span><span class="p">()</span>
</pre></div>
</div>
<p>Answer: use a <em>class method</em> or even better a <em>static method</em>. The
class method:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">MyFantasticClass</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span> <span class="nd">@classmethod</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">interrupt</span><span class="p">(</span> <span class="n">klass</span><span class="p">):</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">'Or a woman !'</span>
<span class="gp">>>> </span><span class="n">MyFantasticClass</span><span class="o">.</span><span class="n">interrupt</span><span class="p">()</span>
<span class="go">Or a woman !</span>
</pre></div>
</div>
<p>For the user of the class, it dos not make much of a difference if the
function is bound to the class or just static, but it changes the
definition. The class method is passed the class as the first argument
(and not <em>self</em>, the instance). In our example, the best choice is a
<em>static</em> method since the function uses neither the instance nor the
class:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">MyFantasticClass</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span> <span class="nd">@staticmethod</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">interrupt</span><span class="p">():</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">'Or a woman !'</span>
<span class="gp">>>> </span><span class="n">MyFantasticClass</span><span class="o">.</span><span class="n">interrupt</span><span class="p">()</span>
<span class="go">Or a woman !</span>
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