Python: Cipher and Base64 Encoding / Decoding

Below is part of a challenge that I came up with to first create like a caesar cipher or rot13 similar cipher and then use base64 to encode a URL.  Below is the python code to accomplish this:

#!/usr/bin/python

import string
import base64

url = "http://i1.ytimg.com/vi/jp4nzjap6I8/movieposter.jpg?v=4f16e5dc"
my_base64chars  = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/"
std_base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

s = url.translate(string.maketrans(my_base64chars, std_base64chars))
data = base64.b64encode(s)
print data

Below is how to decode the same information:

#!/usr/bin/python

import string

import base64

code = "cjMzejovL3NCLjgzc3dxLm15dy81cy90ekV4OXRrekdTSS93eTVzb3p5MjNvMS50enE/NT1FcEJHb0ZubQ=="

output = base64.b64decode(code)

print output

my_base64chars  = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/"

std_base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

s = output.translate(string.maketrans(std_base64chars, my_base64chars))

print s