title: How to merge pandas on string contains?
body: <p>I have 2 dataframes that I would like to merge on a common column. However the column I would like to merge on are not of the same string, but rather a string from one is contained in the other as so:</p>
  
  <pre><code>import pandas as pd
  df1 = pd.DataFrame({'column_a':['John','Michael','Dan','George', 'Adam'], 'column_common':['code','other','ome','no match','word']})
  
  df2 = pd.DataFrame({'column_b':['Smith','Cohen','Moore','K', 'Faber'], 'column_common':['some string','other string','some code','this code','word']})
  </code></pre>
  
  <p>The outcome I would like from <code>d1.merge(d2, ...)</code> is the following:</p>
  
  <pre><code>column_a  |  column_b
  ----------------------
  John      |  Moore    &lt;- merged on 'code' contained in 'some code' 
  Michael   |  Cohen    &lt;- merged on 'other' contained in 'other string'  
  Dan       |  Smith    &lt;- merged on 'ome' contained in 'some string'  
  George    |  n/a
  Adam      |  Faber    &lt;- merged on 'word' contained in 'word'  
  </code></pre>