title: How to allow duplicate column names in pandas DataFrame
body: <p>I have a DataFrame and I want to update column names for this data frame. The column names have duplicate entries. The below code gives error: 'cannot reindex from a duplicate axis.</p>
  <pre><code>list=['alpha', 'beta','gamma', 'alpha']
  df=pd.DataFrame(datframe,columns=list)
  </code></pre>