# -- ceaser_cipher_1.py -- 
# Ceaser cipher encode and decode for problems 8 and 9, 
# page 199 of Zelle's "Python Programming".
#
# This version shifts any ascii character 
# in the range 0 to 127 by a constant amount,
# wrapping around at 128.  (For example, 
# 123 + 10 = 133 mod 128 = 5.)
#
# Running it looks like this:
#
#   $ python ceaser_cipher_1.py 
#   Enter plain text: Once through.
#   Enter numeric key: 6
#   Encoded: Utik&znxu{mn4
#
#   Enter coded text: Utik&znxu{mn4
#   Enter numeric key: 6
#   Decoded: Once through.
#   $
#
# Jim Mahoney, Sep 22 2008, GPL
#

def encode():
  plain_text = raw_input('Enter plain text: ')
  key = input('Enter numeric key: ')
  coded_text = ''
  for char in plain_text:
    char_as_number = ord(char)
    shifted_number = (char_as_number + key) % 128
    new_char = chr(shifted_number)
    coded_text = coded_text + new_char
  print "Encoded: " + coded_text

def decode():
  coded_text = raw_input('Enter coded text: ')
  key = input('Enter numeric key: ')
  plain_text = ''
  for char in coded_text:
    char_as_number = ord(char)
    shifted_number = (char_as_number - key) % 128
    new_char = chr(shifted_number)
    plain_text = plain_text + new_char
  print "Decoded: " + plain_text

encode()
print ""
decode()