title: Get non zero values for each column in pandas
body: <p>I have pandas dataframe as <code>df</code>:</p>
  
  <pre><code>accel access adviser afpif  afp   publish  afraid verizon
  0.00  0.14    0.00   0.00   0.00   0.13    0.00   0.44
  0.13  0.00    0.00   0.77   0.00   0.00    0.22   0.00
  0.00  0.00    0.87   0.00   0.34   0.00    0.00   0.00
  ......................................................
  .....................................................
  </code></pre>
  
  <p>I also have a list <code>L</code> which consist columns names as elements</p>
  
  <pre><code>L=['accel','afp','publish']
  </code></pre>
  
  <p>All I want to extract non zero values of these list elements based on <code>pandas dataframe</code>. </p>
  
  <p>Expected Output:-</p>
  
  <pre><code>dictionary={'accel':0.13,'afp':0.34,'publish':0.13}
  </code></pre>