title: Finding the number of cells with strings containing a particular character
body: <p>I want to know how many cells in each row contain strings with a particular character.  For example:</p>
  
  <pre><code>d = {'a':[1,2,'abc','ace'],'b':['aa','bb','cc',5],'c':['zzz','byy','xxx','wwb']}
  df = pd.DataFrame(d, index=['m','n','o','p'])
  df
  
      a   b   c
  m   1   aa  zzz
  n   2   bb  byy
  o   abc cc  xxx
  p   ace 5   wwb
  </code></pre>
  
  <p>I want to know the number of cells in each row that contain a "b":</p>
  
  <pre><code>    a   b   c   Count
  m   1   aa  zzz 0
  n   2   bb  byy 2
  o   abc cc  xxx 1
  p   ace 5   wwb 1
  </code></pre>
  
  <p><code>str.contains</code> works on Series, not DataFrames. I could step through the index and do something like </p>
  
  <pre><code>df.loc['m','Count'] = df.loc['m'].str.contains('b').sum()
  </code></pre>
  
  <p>but it seems like there should be a much simpler solution that I'm missing right now.</p>