title: Sum of list of lists; returns sum list
body: <p>Let <code>data = [[3,7,2],[1,4,5],[9,8,7]]</code></p>
  
  <p>Let's say I want to sum the elements for the indices of each list in the list, like adding numbers in a matrix column to get a single list. I am assuming that all lists in data are equal in length.</p>
  
  <pre><code>    print foo(data)
  
     [[3,7,2],
      [1,4,5],
      [9,8,7]]
      _______
   &gt;&gt;&gt;[13,19,14]
  </code></pre>
  
  <p>How can I iterate over the list of lists without getting an index out of range error? Maybe lambda? Thanks!</p>