code: def unshorten_url(short_url):
      
      short_url = short_url.strip()
      if not short_url.startswith('http'):
          short_url = 'http://{0}'.format(short_url)
  
      try:
          cached_url = UnshortenURL.objects.get(short_url=short_url)
      except UnshortenURL.DoesNotExist:
          cached_url = UnshortenURL(short_url=short_url)
      else:
          return cached_url.long_url
  
      try:
          resp = urllib2.urlopen(short_url)
      except (
              urllib2.HTTPError, urllib2.URLError,
              httplib.HTTPException):
          return None
  
      if resp.code == 200:
          cached_url.long_url = resp.url
          cached_url.save()
          return resp.url
docs: Unshortens the short_url or returns None if not possible.