title: Python : Compare two csv files and print out differences
body: <p>I need to compare two CSV files and print out differences in a third CSV file.
  In my case, the first CSV is a old list of hash named old.csv and the second CSV is the new list of hash which contains both old and new hash.</p>
  
  <p>Here is my code :</p>
  
  <pre><code>import csv
  t1 = open('old.csv', 'r')
  t2 = open('new.csv', 'r')
  fileone = t1.readlines()
  filetwo = t2.readlines()
  t1.close()
  t2.close()
  
  outFile = open('update.csv', 'w')
  x = 0
  for i in fileone:
      if i != filetwo[x]:
          outFile.write(filetwo[x])
      x += 1
  outFile.close()
  </code></pre>
  
  <p>The third file is a copy of the old one and not the update.
  What's wrong ? I Hope you can help me, many thanks !! </p>
  
  <p>PS : i don't want to use diff </p>