Python - Error al encriptar

import binascii

import itertools

import base64

import sys

def xor_crypt_string(data, key = 'estoesunaclaveparacifrar', encode = False, decode = False):

	from itertools import zip, cycle

	import base64

	if decode:

		data = base64.decodestring(data)

	xored = ''.join((chr(ord(x) ^ ord(y)) for x, y in zip(data,cycle(key))))

	if encode:

		return base64.encodestring(xored).strip()

	return xored

secret_data = sys.argv[0]

print ('Cifrado')

print xor_crypt_string(secret_data, encode=True)

print ('Descifrado')

print xor_crypt_string(xor_crypt_string(secret_data, encode=True), decode=True)

print ('Cifrado')

print (xor_crypt_string(secret_data, encode=True))

print ('Descifrado')

print (xor_crypt_string(xor_crypt_string(secret_data, encode=True), decode=True))