title: pandas DataFrame reset_index which can handle duplicate column names?
body: <p>Is there any equivalent of <code>pandas.DataFrame.reset_index()</code> which operates on the columns and can handle the case of duplicate column names? I want it to throw away the column names and return a default numbered index 0,1,2.. for the columns. (Methods like <code>df.rename</code> or <code>df.reindex_axis</code> do not work when I have duplicate column names.)</p>
  
  <p>Sample input:</p>
  
  <pre><code> pd.DataFrame(np.random.rand(5, 3), columns = ['A', 'A', 'B'])
  
       A   A   B
  0   0.5 0.3 0.9
  1   0.7 0.9 0.3
  2   0.9 0.4 0.8
  3   0.6 0.2 0.9
  4   0.7 0.4 0.6
  </code></pre>
  
  <p>Expected output:</p>
  
  <pre><code>     0   1   2
  0   0.8 0.1 0.2
  1   0.4 0.2 0.4
  2   0.3 0.3 0.4
  3   0.4 0.1 0.8
  4   1.0 0.9 0.9
  </code></pre>