title: Finding elements in a pandas dataframe
body: <p>I have a pandas dataframe which looks like the following:</p>
  
  <pre><code>0 1
  0 2
  2 3
  1 4
  </code></pre>
  
  <p>What I want to do is the following: if I get 2 as input my code is supposed to search for 2 in the dataframe and when it finds it returns the value of the other column. In the above example my code would return 0 and 3. I know that I can simply look at each row and check if any of the elements is equal to 2 but I was wondering if there is one-liner for such a problem.</p>
  
  <p>UPDATE: None of the columns are index columns.</p>
  
  <p>Thanks</p>