title: How to create a pandas column with words from another column, contained in a list
body: <p>I want to strip words, specified in a list, from stings of a pandas column, and build another column with them.
  I have this example inspired from question <a href="https://stackoverflow.com/questions/43055050/python-pandas-if-column-string-contains-word-flag/43055068#43055068">python pandas if column string contains word flag</a></p>
  <pre class="lang-py prettyprint-override"><code>listing  = ['test', 'big']
  df = pd.DataFrame({'Title':['small test','huge Test', 'big','nothing', np.nan, 'a', 'b']})
  df['Test_Flag'] = np.where(df['Title'].str.contains('|'.join(listing), case=False, 
  na=False), 'T', '')
  print (df)
  </code></pre>
  <pre><code>        Title         Test_Flag
  0  small test         T
  1  huge Test          T
  2  big                T
  3  nothing
  4   NaN          
  5     a
  6     b
  </code></pre>
  <p>But, what if I want to put instead of &quot;T&quot;, the actual word in the list that has been found?
  So, having a result:</p>
  <pre><code>        Title       Test_Flag
  0  small test       test
  1  huge Test        test
  2  big              big
  3  nothing
  4   NaN          
  5     a
  6     b
  </code></pre>