title: Summarized Data frame with conditional calculation. Pandas
body: <p>How to summarized Data frame with conditional calculation.</p>
  <p>Based on col1 values find ratio for count of negatives of total count for it.</p>
  <p>Example:</p>
  <pre><code>Col1    Col2  
  --------------
   A       0.5
   A       0.3
   A      -0.6
   B      -0.3
   C      -0.2
   B         0
   C      -0.1
  
  
  data = {'Col1':['A','A','A','B','C','B','C'],
          'Col2':[0.5,0.3,-0.6,-0.3,-0.2,0,-0.1]}
  
  For A
  Total number of negative (Count) / Total count for A 
  = 1/3 = 0.33
  </code></pre>
  <p>Expected Result:</p>
  <pre><code>Col1    Col2  
  --------------
   A       0.33
   B       0.5
   C       1
  </code></pre>