title: Use Pandas string method 'contains' on a Series containing lists of strings
body: <p>Given a simple Pandas Series that contains some strings which can consist of more than one sentence:</p>
  
  <pre><code>In:
  import pandas as pd
  s = pd.Series(['This is a long text. It has multiple sentences.','Do you see? More than one sentence!','This one has only one sentence though.'])
  
  Out:
  0    This is a long text. It has multiple sentences.
  1                Do you see? More than one sentence!
  2             This one has only one sentence though.
  dtype: object
  </code></pre>
  
  <p>I use pandas string method <code>split</code> and a regex-pattern to split each row into its single sentences (which produces unnecessary empty list elements - any suggestions on how to improve the regex?).</p>
  
  <pre><code>In:
  s = s.str.split(r'([A-Z][^\.!?]*[\.!?])')
  
  Out:
  0    [, This is a long text.,  , It has multiple se...
  1        [, Do you see?,  , More than one sentence!, ]
  2         [, This one has only one sentence though., ]
  dtype: object
  </code></pre>
  
  <p>This converts each row into lists of strings, each element holding one sentence.</p>
  
  <p>Now, my goal is to use the string method <code>contains</code> to check each element in each row seperately to match a specific regex pattern and create a new Series accordingly which stores the returned boolean values, each signalizing if the regex matched on at least one of the list elements.</p>
  
  <p>I would expect something like:</p>
  
  <pre><code>In:
  s.str.contains('you')
  
  Out:
  0   False
  1   True
  2   False
  </code></pre>
  
  <p>&lt;-- Row 0 does not contain <code>'you'</code> in any of its elements, but row 1 does, while row 2 does not.</p>
  
  <p>However, when doing the above, the return is</p>
  
  <pre><code>0   NaN
  1   NaN
  2   NaN
  dtype: float64
  </code></pre>
  
  <p>I also tried a list comprehension which does not work:</p>
  
  <pre><code>result = [[x.str.contains('you') for x in y] for y in s]
  AttributeError: 'str' object has no attribute 'str'
  </code></pre>
  
  <p>Any suggestions on how this can be achieved?</p>