title: Pandas - move values of a column under another column
body: <p>So here is my problem.</p>
  <p>I'm using pandas to parse csv file.</p>
  <p>So my csv file looks like this :</p>
  <pre><code>A   B   C   D
  1   x   5   e
  2   y   6   f
  3   z   7   g
  </code></pre>
  <p>What I want to get is :</p>
  <ol>
  <li>get all the values of column C</li>
  <li>Place them under column A</li>
  <li>Same with columns D and B</li>
  </ol>
  <p>So it would get me this :</p>
  <pre><code>A   B   C   D
  1   x       
  2   y       
  3   z      
  5   e
  6   f
  7   g
  </code></pre>
  <p>However, all i've been able to get is to create a new column that &quot;sums&quot; column A with column C and column B with column D:</p>
  <pre><code>A   B   C   D   E   F
  1   x   5   e   15  xe
  2   y   6   f   26  yf
  3   z   7   g   37  zg
  </code></pre>
  <p>Any idea would be appreciated.</p>
  <p>Thanks</p>