title: Extracting strings from a pattern in a pandas dataframe
body: <p>i have a dataframe with a column full of strings as follows:</p>
  
  <p><code>1                    Janus Henderson Research Fund Class N
  2                              Calvert Equity Fund Class A
  3               Invesco Diversified Dividend Fund R5 Class
  4                    Prudential Day One 2035 Fund Class R3
  5                TETON Convertible Securities Fund Class C
                                 ...<br>
  24991              BlackRock Asian Dragon Fund,Inc.Class R
  24993    MFS Blended Research International Equity Fund...
  24994                   ClearBridge Small Cap Fund Class A
  24995    Federated Equity Income Fund, Inc. Class A Shares</code></p>
  
  <p>im looking to extract the class of each of the rows.
  for example row 1,  as class N, row 2 as classA and so on.. some of the rows do not have the word class all together, which i would like to be NA. also some of the rows have the class label before the word class. how do i go about extracting this ? 
  any guidance is appreciated </p>