title: How to print the comparison of two multiline strings in unified diff format?
body: <p>Do you know any library that will help doing that?</p>
  
  <p>I would write a function that prints the differences between two multiline strings in the unified diff format. Something like that:</p>
  
  <pre><code>def print_differences(string1, string2):
      """
      Prints the comparison of string1 to string2 as unified diff format.
      """
      ???
  </code></pre>
  
  <p>An usage example is the following:</p>
  
  <pre><code>string1="""
  Usage: trash-empty [days]
  
  Purge trashed files.
  
  Options:
    --version   show program's version number and exit
    -h, --help  show this help message and exit
  """
  
  string2="""
  Usage: trash-empty [days]
  
  Empty the trash can.
  
  Options:
    --version   show program's version number and exit
    -h, --help  show this help message and exit
  
  Report bugs to http://code.google.com/p/trash-cli/issues
  """
  
  print_differences(string1, string2)
  </code></pre>
  
  <p>This should print something like that:</p>
  
  <pre><code>--- string1 
  +++ string2 
  @@ -1,6 +1,6 @@
   Usage: trash-empty [days]
  
  -Purge trashed files.
  +Empty the trash can.
  
   Options:
     --version   show program's version number and exit
  </code></pre>