#!/usr/bin/env python

from string import uppercase, lowercase, maketrans
import sys

class ROTAlpha():

  def rot_alpha(self, data, rot):

    upper = ''.join([uppercase[(i+rot)%26] for i in xrange(26)])
    lower = ''.join([lowercase[(i+rot)%26] for i in xrange(26)])
    table = maketrans(uppercase + lowercase, upper + lower)

    print(data.translate(table))


if __name__ == '__main__':
  try:

    data = sys.argv[1]
    rot = sys.argv[2]
    rot = int(rot, 0)
    table = ROTAlpha()
    table.rot_alpha(data, rot)

  except IndexError:

    print('Usage: rot_alpha.py <alpha numeric data> <int to rotate>')
    sys.exit(1)

Create rot_alpha.py