title: pandas map one column to the combination of two columns
body: <p>I am working with a <code>DataFrame</code> which looks like this</p>
  
  <pre><code>List    Numb    Name
  1       1       one
  1       2       two
  2       3       three
  4       4       four
  3       5       five
  </code></pre>
  
  <p>and I am trying to compute the following output.</p>
  
  <pre><code>List    Numb    Name
  one     1       one
  one     2       two
  two     3       three
  four    4       four
  three   5       five
  </code></pre>
  
  <p>In my current approach I'm trying to iterate through the columns, then replace values with the contents of a third column.</p>
  
  <p>For example, if <code>List[0][1]</code> is equal to <code>Numb[1][1]</code> replace column <code>List[0][1]</code> with <code>'one'</code>.</p>
  
  <p>How could I make an iteration like this work, or alternatively solve the problem without explicitly iterating at all?</p>