title: Group data from a CSV file by field value
body: <p>I have a csv file which has duplicate value in first column . I want to collect all value of second column in a list  for one value of first column</p>
  
  <pre><code>column1 column2
  a        54.2
  s        78.5
  k        89.62
  a        77.2
  a        65.56
  </code></pre>
  
  <p>I want to get like</p>
  
  <pre><code>print a  # [54.2,77.2,65.56]
  print s  # [78.5]
  print k  # [89.62]
  </code></pre>