code: def dist(self, src, tar, diff_lens=True):
          
          if src == tar:
              return 0.0
          return self.dist_abs(src, tar, diff_lens) / max(len(src), len(tar))
docs: Return the normalized Hamming distance between two strings.
  
          Hamming distance normalized to the interval [0, 1].
  
          The Hamming distance is normalized by dividing it
          by the greater of the number of characters in src & tar (unless
          diff_lens is set to False, in which case an exception is raised).
  
          The arguments are identical to those of the hamming() function.
  
          Parameters
          ----------
          src : str
              Source string for comparison
          tar : str
              Target string for comparison
          diff_lens : bool
              If True (default), this returns the Hamming distance for those
              characters that have a matching character in both strings plus the
              difference in the strings' lengths. This is equivalent to extending
              the shorter string with obligatorily non-matching characters. If
              False, an exception is raised in the case of strings of unequal
              lengths.
  
          Returns
          -------
          float
              Normalized Hamming distance
  
          Examples
          --------
          >>> cmp = Hamming()
          >>> round(cmp.dist('cat', 'hat'), 12)
          0.333333333333
          >>> cmp.dist('Niall', 'Neil')
          0.6
          >>> cmp.dist('aluminum', 'Catalan')
          1.0
          >>> cmp.dist('ATCG', 'TAGC')
          1.0