Over-engineered Rock Paper Scissors game

rps.py

#!/usr/bin/env python2.6

class RPSObject(object):
    def __init__(self, name):
        self.name = name
        self.beats = []
        self.loses_to = []

    def against(self, opponent):
        if opponent in self.loses_to:
            print("Opponent %s beats %s" % (opponent, self))
        elif opponent in self.beats:
            print("%s beats opponent %s" % (self, opponent))
        elif opponent == self:
            print("Draw between %s and opponent %s" % (self, opponent))
        else:
            raise ValueError("%s vs %s not defined")

    def __gt__(self, b):
        if b in self.loses_to:
            raise ValueError("%s can't both beat and lose to %s" % (self, b))
        
        self.beats.append(b)
        b.loses_to.append(self)

    def __lt__(self, b):
        if b in self.beats:
            raise ValueError("%s can't both beat and lose to %s" % (self, b))
        
        self.loses_to.append(b)
        b.beats.append(self)
    
    def __repr__(self):
        return "<%s>" % (self.name)


def main():
    # Set up the game objects
    rock = RPSObject('rock')
    paper = RPSObject('paper')
    scissors = RPSObject('scissors')

    # Define rules
    rock > scissors
    paper > rock
    scissors > paper

    # A few fixed games
    scissors.against(paper)
    scissors.against(rock)
    scissors.against(scissors)
    rock.against(scissors)
    
    # Play a random object against rock
    import random
    random.choice([rock, paper, scissors]).against(rock)


if __name__ == '__main__':
    main()