title: Add constant value column that changes half way down to pandas dataframe
body: <p>I have the list:</p>
  
  <pre><code>[['abc', 1, 2, 3], ['bfg', 4, 5, 6], ['abc', 7, 8, 9], ['bfg', 10, 11, 12]]
  </code></pre>
  
  <p>And I make it into a pandas DataFrame, which returns (after adding a column with the color <code>lst[4] = 'blue'</code>):</p>
  
  <pre><code>     0   1   2   3     4
  0  abc   1   2   3  blue
  1  bfg   4   5   6  blue
  2  abc   7   8   9  blue
  3  bfg  10  11  12  blue
  </code></pre>
  
  <p>Is there anyway to make it return this instead:</p>
  
  <pre><code>     0   1   2   3     4
  0  abc   1   2   3  blue
  1  bfg   4   5   6  blue
  2  abc   7   8   9  red
  3  bfg  10  11  12  red
  </code></pre>