title: convert a column in a python pandas from STRING MONTH into INT
body: <p>In Python 2.7.11 &amp; Pandas 0.18.1:</p>
  
  <p>If we have the following csv file:</p>
  
  <pre><code>YEAR,MONTH,ID
  2011,JAN,1
  2011,FEB,1
  2011,MAR,1
  </code></pre>
  
  <p>Is there any way to read it as a Pandas data frame and convert the MONTH column into strings like this?</p>
  
  <pre><code>YEAR,MONTH,ID
  2011,1,1
  2011,2,1
  2011,3,1
  </code></pre>
  
  <p>Some pandas functions such as "dt.strftime('%b')" doesn't seem to work.  Could someone enlighten?  </p>