title: Adding element to list in pandas column
body: <p>I can't figure out how to add element to pandas column for single row.</p>
  
  <pre><code>index = ['a','b','c','d']
  df = pd.DataFrame(index = index)
  df['Col'] = [[]] * len(index)
  
  df.loc['d','Col'].append('AA')
  </code></pre>
  
  <p>returns:</p>
  
  <pre><code>    Col
  a   [AA]
  b   [AA]
  c   [AA]
  d   [AA]
  </code></pre>
  
  <p>I look for value 'AA' to be in the last row only.</p>