title: Pandas: Multiple columns into one column
body: <p>I have the following data (2 columns, 4 rows):</p>
  
  <pre><code>Column 1: A, B, C, D
  
  Column 2: E, F, G, H
  </code></pre>
  
  <p>I am attempting to combine the columns into one column to look like this (1 column, 8 rows):</p>
  
  <pre><code>Column 3: A, B, C, D, E, F, G, H
  </code></pre>
  
  <p>I am using pandas DataFrame and have tried using different functions with no success (<code>append</code>, <code>concat</code>, etc.). Any help would be most appreciated!</p>