title: Pandas remove column by index
body: <p>Suppose I have a DataFrame like this:</p>
  
  <pre><code>&gt;&gt;&gt; df = pd.DataFrame([[1,2,3], [4,5,6], [7,8,9]], columns=['a','b','b'])
  &gt;&gt;&gt; df
     a  b  b
  0  1  2  3
  1  4  5  6
  2  7  8  9
  </code></pre>
  
  <p>And I want to remove second <code>'b'</code> column. If I just use <code>del</code> statement, it'll delete both <code>'b'</code> columns:</p>
  
  <pre><code>&gt;&gt;&gt; del df['b']
  &gt;&gt;&gt; df
     a
  0  1
  1  4
  2  7
  </code></pre>
  
  <p>I can select column by index with <code>.iloc[]</code> and reassign DataFrame, but how can I delete only second <code>'b'</code> column, for example by index?</p>