title: How to prepend pandas data frames
body: <p>How can I prepend a dataframe to another dataframe? Consider dataframe A:</p>
  
  <pre><code>b c d
  2 3 4
  6 7 8
  </code></pre>
  
  <p>and dataFrame B:</p>
  
  <pre><code>a
  1
  5
  </code></pre>
  
  <p>I want to prepend A to B to get:</p>
  
  <pre><code>a b c d
  1 2 3 4
  5 6 7 8
  </code></pre>