title: How to append a list to pandas column, series?
body: <p>Asume that I have the following dataframe:</p>
  
  <pre><code>d = {'col1': [1, 2], 'col2': [3, 4]}
  df = pd.DataFrame(data=d)
  </code></pre>
  
  <p>I would like to extend <code>col1</code> with array <code>xtra</code>. However this errors out.</p>
  
  <pre><code>xtra = [3,4]
  df['col1'].append(xtra)
  </code></pre>
  
  <p>How can I append <code>xtra</code> to <code>df.col1</code>, so that the final otuput would looks as so?</p>
  
  <pre><code>   col1  col2
  0     1     3
  1     2     4
  2     3     nan
  3     4     nan
  </code></pre>