difference between 'is' and '=='
<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="http://stackoverflow.com/questions/26595/is-there-any-difference-between-foo-is-none-and-foo-none">Is there any difference between &ldquo;foo is None&rdquo; and &ldquo;foo == None&rdquo;?</a>  </p>
</blockquote>



<p>Quite a simple question really.</p>

<p>Whats the difference between:</p>

<pre><code>if a.b is 'something':
</code></pre>

<p>and</p>

<pre><code>if a.b == 'something':
</code></pre>

<p>excuse my ignorance</p>
