new communication protocol checker for jesse farmer!

everlane_comm.py

#-------------------------------------------------------------------------------
# new communication protocol checker for jesse farmer!
#
# Author:      ayumi yu
# Created:     06.10.2011
# Last mod:    08.10.2011
# Licence:     MIT
#-------------------------------------------------------------------------------
#!/usr/bin/env python

# ** imports and stuff
import string

# ** FUNctions
def checkValid( message ):
    """
    Check if a message is valid according to the protocol.
    The message is assumed to have only the 15 valid characters (a-j, ZMKPQ)
    """
    # > Invalidation
    # Rightmost char must be a-j; they're the only independently valid messages
    if message[ len(message)-1: ] not in list(string.ascii_lowercase[:10]):
        return False

    # Second to last char cannot be KMPQ, that requires at least 2 more chars after
    elif message[ len(message)-2 : len(message)-1] in ['K','M','P','Q']:
        return False

    # > Validation
    # Single characters a-j are valid
    elif message in list(string.ascii_lowercase[:10]):
        return True

    # If Zxx then check if the xx is a valid message
    elif message[:1] == 'Z' and len(message) >= 2 and checkValid(message[1:]):
        return True

    # If Myy/Kyy/Pyy/Qyy check if yy can be split into 2 valid messages
    elif message[:1] in ['K','M','P','Q'] and len(message) >= 3:
        # Divide in 2, in all possible ways and check the pairs
        for x in range(2, len(message)):
            if checkValid( message[1:x] ) and checkValid(message[x:]):
                return True

    # > Failed to validate. Return invalid by default
    else:
        return False


# Logic begins!
testInput = raw_input("Input, please! ")

# Go through each message split by whitespace
for message in testInput.split():
    result = 'VALID' if checkValid(message) else 'INVALID'
    print "%s %s" % ( message, result )