title: Python leading underscore _variables
body: <p>We know that in a class, functions starting with <code>__function__</code> do not get imported while using:</p>
  
  <pre><code>from module import *
  </code></pre>
  
  <p>Someone asked what is an <code>_variable</code>? I have never used one.<br>
  Do they exist?  Is this a concept of variable which cannot be accessed using class object or something? </p>