title: calculate percentage of strings instead of statistics
body: <p>I would like to calculate the percentage of each letter in my file instead of the number. How can I modify the following code?</p>
  
  <pre><code>stat_file = open(filename, 'w')
  one_letter = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  for letter in one_letter:
      stat_file.writelines('%s : %d \n' % (letter, statistics[letter]))
  </code></pre>
  
  <p>Thanks in advance!</p>