title: Percentage function on bool series in Pandas
body: <p>Using a function similar to this:</p>
  
  <pre><code>def percentage(part, whole):
      return 100 * float(part)/float(whole)
  </code></pre>
  
  <p>I can get the percentage calling the function:</p>
  
  <pre><code>percentage(215,413)
  </code></pre>
  
  <p>But how do I take a bool series and get the percentage of True and False?</p>
  
  <pre><code>s = pd.Series(np.random.randn(5) +5)
  
  s &gt; 5
  
  0     True
  1    False
  2    False
  3     True
  4     True
  dtype: bool
  </code></pre>
  
  <p>Desired output is percentage of True values in the series (60% in the example above).  Do I need to <code>map</code> a function to get the output?  Please show me the best way to do this.  thanks</p>