code: def countPrint(mesg, count, len1, len2=None):
      
      def percentage(a, b):
          """
          What percent of a is b?
  
          @param a: a numeric value.
          @param b: a numeric value.
          @return: the C{float} percentage.
          """
          return 100.0 * a / b if b else 0.0
  
      if count == 0:
          return '%s: %d' % (mesg, count)
      else:
          len2 = len2 or len1
          if len1 == len2:
              return '%s: %d/%d (%.2f%%)' % (
                  mesg, count, len1, percentage(count, len1))
          else:
              return ('%s: %d/%d (%.2f%%) of sequence 1, '
                      '%d/%d (%.2f%%) of sequence 2' % (
                          mesg,
                          count, len1, percentage(count, len1),
                          count, len2, percentage(count, len2)))
docs: Format a message followed by an integer count and a percentage (or
      two, if the sequence lengths are unequal).
  
      @param mesg: a C{str} message.
      @param count: a numeric value.
      @param len1: the C{int} length of sequence 1.
      @param len2: the C{int} length of sequence 2. If C{None}, will
          default to C{len1}.
      @return: A C{str} for printing.