What is the difference in python attributes with underscore in front and back
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/1301346/the-meaning-of-a-single-and-a-double-underscore-before-an-object-name-in-python">The meaning of a single- and a double-underscore before an object name in Python</a>  </p>
</blockquote>



<p>I want to know what is the different between these in python</p>

<p><code>self._var1</code></p>

<p><code>self._var1_</code></p>

<p><code>self.__var1</code></p>

<p><code>self.__var1__</code></p>
