Learning to program with Rock, Paper, Scissors, Lizard, Spock; a class based version with an indexed data store for reference.

rpsls.py

#!/usr/bin/env python
"""
The idea of this program is to equate the strings "rock", "paper", 
"scissors", "lizard", "Spock" to numbers as follows:

0 - rock
1 - Spock
2 - paper
3 - lizard
4 - scissors
"""

import random 

class RPSLS(object):
    
    data = ["rock", "Spock", "paper", "lizard", "scissors"]

    def number_to_name(self, idx):
        """
        Given a number, convert to the name
        """
        return self.data[idx]

    def name_to_number(self, name):
        """
        Given a name, convert to the number
        """
        for idx, val in enumerate(self.data):
            if name == val: return idx
        return None

    def computer_guess(self):
        return random.randrange(0, 4)

    def play(self, name):
        """
        Play your hand against the computer to see who wins!
        
        rock     > lizard, scissors
        Spock    > rock, paper
        paper    > rock, lizard
        lizard   > scissors, Spock
        scissors > paper, Spock
        """
        
        player = self.name_to_number(name)
        robot  = self.computer_guess()
        winner = (player - robot) % len(self.data)
        
        output = "Player plays '%s'\tRobot plays '%s'\tWinner: %s" 

        if winner == 0:
            # Result is 0
            winner = "Tie"

        elif winner % 2 == 0:
            # Result is even
            winner = "Player"
        
        else:
            # Result is odd
            winner ="Robot"

        player = self.number_to_name(player)
        robot  = self.number_to_name(robot)

        return output % (player, robot, winner)

if __name__ == "__main__":

    game = RPSLS()

    print game.play("rock")
    print game.play("Spock")
    print game.play("paper")
    print game.play("lizard")
    print game.play("scissors")