title: Where can I find the _sre.py python built-in module?
body: <p>I am studying the  python regular expression (<code>re.py</code>) source code.</p>
  
  <p>In <code>re.py</code> they imported the module <code>sre_compile</code>:</p>
  
  <pre><code>import sre_compile
  </code></pre>
  
  <p>and I look at the module sre_compile there they imported the module <code>_sre</code>  in the line 13</p>
  
  <pre><code>import _sre, sys
  </code></pre>
  
  <p>I searched for the module <code>_sre.py</code> but I could not find it anywhere, I even tried to<br>
  locate <code>_sre.py</code> in my shell.</p>
  
  <p>In the end I tried to locate it with the python interpreter. I imported <code>_sre</code> and I was trying to look for the <code>__file__</code> attribute of <code>_sre</code> but it gave me the following error: </p>
  
  <pre><code>AttributeError: 'module' object has no attribute '__file__'
  </code></pre>
  
  <p>Where can I find the <code>_sre</code> module source code?</p>