crypto program in python.

[khudo.anastasia at gmail.com]

Hi every every body,
Today I have to submit my assignment for Computer Science, And I am absolutely stuck in writing the code. Please help me in soon possible.

The main idea of the program is encode and decode the text.
that wot the instructor gave us so far.

Sample Run

Here's a sample run of the basic program in action.

  SECRET DECODER MENU
  
  0) Quit
  1) Encode
  2) Decode
  
What do you want to do? 1
text to be encoded: python rocks
AQULEWKEMNJ

  
  SECRET DECODER MENU
  
  0) Quit
  1) Encode
  2) Decode
  
What do you want to do? 2
code to be decyphered: AQULEWKEMNJ
PYTHONROCKS

  
  SECRET DECODER MENU
  
  0) Quit
  1) Encode
  2) Decode
  
What do you want to do? 0
Thanks for doing secret spy stuff with me.
-----------------------------------
and


alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
key =   "XPMGTDHLYONZBWEARKJUFSCIQV"

def main():
  keepGoing = True
  while keepGoing:
    response = menu()
    if response == "1":
      plain = raw_input("text to be encoded: ")
      print encode(plain)
    elif response == "2":
      coded = raw_input("code to be decyphered: ")
      print decode(coded)
    elif response == "0":
      print "Thanks for doing secret spy stuff with me."
      keepGoing = False
    else:
      print "I don't know what you want to do..."

-------------------

I am confused about menu and the str function if you can help me with this code it will be awesome thank you!!!