code: def dist_abs(self, src, tar, diff_lens=True):
          
          if not diff_lens and len(src) != len(tar):
              raise ValueError(
                  'Undefined for sequences of unequal length; set diff_lens '
                  + 'to True for Hamming distance between strings of unequal '
                  + 'lengths.'
              )
  
          hdist = 0
          if diff_lens:
              hdist += abs(len(src) - len(tar))
          hdist += sum(c1 != c2 for c1, c2 in zip(src, tar))
  
          return hdist
docs: Return the Hamming distance between two strings.
  
          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
          -------
          int
              The Hamming distance between src & tar
  
          Raises
          ------
          ValueError
              Undefined for sequences of unequal length; set diff_lens to True
              for Hamming distance between strings of unequal lengths.
  
          Examples
          --------
          >>> cmp = Hamming()
          >>> cmp.dist_abs('cat', 'hat')
          1
          >>> cmp.dist_abs('Niall', 'Neil')
          3
          >>> cmp.dist_abs('aluminum', 'Catalan')
          8
          >>> cmp.dist_abs('ATCG', 'TAGC')
          4