title: Append a string item to lists in a Pandas Column
body: <p>For a pandas dataframe:</p>
  
  <pre><code>Name:        Tags:
  'One'        ['tag1', 'tag3']
  'Two'        []
  'Three'      ['tag1']
  </code></pre>
  
  <p>How can 'tag2' be appended to the tags lists?</p>
  
  <p>I have tried the following (addtag2 is another df):</p>
  
  <pre><code>df['Tags'] = df['Tags'].astype(str) + ', ' + addtag2['Tags'].astype(str)
  </code></pre>
  
  <p>and</p>
  
  <pre><code>df['Tags'] = df['Tags'].add(addtag2['Tags'].astype(str))
  </code></pre>
  
  <p>But they append the string outside the list eg <em>['tag1'], tag2 or ['tag1']tag2</em></p>
  
  <p>The desired output would be:</p>
  
  <pre><code>Name:        Tags:
  'One'        ['tag1', 'tag3', 'tag2']
  'Two'        ['tag2']
  'Three'      ['tag1', 'tag2']
  </code></pre>