title: finding non-unique elements in list not working
body: <p>I wanted to find the non-unique elements in the list, but I am not able to figure out why this is not happening in the below code section.</p>
  
  <pre><code>&gt;&gt;&gt; d = [1, 2, 1, 2, 4, 4, 5, 'a', 'b', 'a', 'b', 'c', 6,'f',3]
  &gt;&gt;&gt; for i in d:
  ...     if d.count(i) == 1:
  ...             d.remove(i)
  ... 
  &gt;&gt;&gt; d
  [1, 2, 1, 2, 4, 4, 'a', 'b', 'a', 'b', 6, 3]
  </code></pre>
  
  <p>6 and 3 should have been removed. 
  where as, if I use </p>
  
  <pre><code>d = [1, 2, 1, 2, 4, 4, 5, 'a', 'b', 'a', 'b', 'c']
  </code></pre>
  
  <p>I am getting correct answer. Please explain what is happening, I am confused !!!</p>
  
  <p>I am using python 2.7.5.</p>