title: Rename column by column index pandas dataframe
body: <p>I would like to rename column 1 of the following dataframe as 'Ref'.
  I have many columns and thus can't rename each or set names for each.</p>
  
  <pre><code>data = [['TC1', 103, 563], ['TC2', 1567, 1290], ['TC3', 1467, 567]] 
  
  dftrash=pd.DataFrame(data, columns = ['Card', '', '']) 
  </code></pre>
  
  <p>This is the dataframe</p>
  
  <pre><code>    Card        
  0   TC1 1037    8563
  1   TC2 1567    1290
  2   TC3 1467    567
  </code></pre>
  
  <p>Now I want to rename the 1st column as 'Ref'.
  I tried this</p>
  
  <pre><code>dftrash.rename(columns={dftrash.columns[1]:'REF'},inplace=True)
  
  </code></pre>
  
  <p>which renames all columns with similar heading as column[1].</p>
  
  <pre><code>
      Card REF    REF
  0   TC1 1037    8563
  1   TC2 1567    1290
  2   TC3 1467    567
  </code></pre>