title: Python - Calculate field density in csv/tsv file
body: <p>Hi suppose if i have a tab seperated file like this (each field separated by tab spaces): </p>
  
  <pre><code>Name    ID    Country    GPA
  Tom    id1    USA        3.4
  Jon    id2    Canada    
  Amy           UK         3.0
  Kevin  id4    Scotland    
  Kris                     3.1
  </code></pre>
  
  <p>Here the density of name = 1.0 that is 100% 
  density of ID is 0.6 that is 60%  (2 fields missing)
  density of Country is 0.8 
  density of GPA is also 0.6</p>
  
  <p>How to find this out for for a file using python? Also I need an algo that's efficient and fast since I need to do this for thousands of files worth more than 40 GB. Map reduce code also works.<br>
  Thanks in advance  :) </p>