title: Sum values of array using zip
body: <p>i have array of arrays this way. 
  I wanna sum a specific fild (like 3rd in the list )</p>
  
  <pre><code>data = [[d, 408.56087701, 87.26907024],
          [b, 277.95015117, 75.19386881],
          [b, 385.41416264, 84.73488504],
          [b, 380.31630662, 71.23504808],
          [b, 392.10729207, 83.80720357],
          [b, 399.70877373, 76.59640833],
          [b, 350.93124656, 79.34979059],
          [b, 330.09702335, 79.37166555]]
  </code></pre>
  
  <p>I am trying this, but it produces problem as I have to select only 3rd in the list (first field is string)</p>
  
  <pre><code>data = [sum(x) for x in zip(*data)]
  </code></pre>
  
  <p>I have to add condition to show that x is third in sub list.</p>