new_contents: class Solution(object):
      def findTheDifference(self, s, t):
          """
          :type s: str
          :type t: str
          :rtype: str
          """
          import itertools
          
          for c1, c2 in itertools.izip_longest(sorted(s), sorted(t)):        
              c1 = c1 if c1 else ''
              c2 = c2 if c2 else ''
              
              if c1 != c2:
                  if len(s) > len(t):
                      return c1
                  else:
                      return c2
                      
          return None
  
subject: Create solution2.py