Rock paper scissors in Python (dict rules, score)

The player types a move, the computer picks one at random, and a dictionary of rules decides who wins. Each key is a move and its value is the move it beats.

The program

python

import random

random.seed(17)  # fixed seed so the output matches this page; remove it for real use

beats = {"rock": "scissors", "paper": "rock", "scissors": "paper"}
moves = list(beats)

rounds = 5
round_number = 1
player_score = 0
computer_score = 0

while round_number <= rounds:
    player = input(f"Round {round_number}. rock, paper or scissors? ").strip().lower()
    if player not in beats:
        print("Please type rock, paper or scissors.")
        continue

    computer = random.choice(moves)
    print(f"The computer chose {computer}.")

    if player == computer:
        print("Draw.")
    elif beats[player] == computer:
        print("You win this round.")
        player_score += 1
    else:
        print("The computer wins this round.")
        computer_score += 1
    round_number += 1

print(f"Final score: you {player_score}, computer {computer_score}")
if player_score > computer_score:
    print("You win the game!")
elif player_score < computer_score:
    print("The computer wins the game.")
else:
    print("The game is a draw.")

Typed in this example: rock, Paper, lizard, scissors, paper, rock. Press Run to type your own.

output

Round 1. rock, paper or scissors? rock
The computer chose scissors.
You win this round.
Round 2. rock, paper or scissors? Paper
The computer chose paper.
Draw.
Round 3. rock, paper or scissors? lizard
Please type rock, paper or scissors.
Round 3. rock, paper or scissors? scissors
The computer chose paper.
You win this round.
Round 4. rock, paper or scissors? paper
The computer chose paper.
Draw.
Round 5. rock, paper or scissors? rock
The computer chose paper.
The computer wins this round.
Final score: you 2, computer 1
You win the game!

How it works

beats[player] == computer asks one question: "is the computer's move the one my move beats?" If yes, the player wins. If the moves are equal, it is a draw. Every other case is a loss. One dictionary replaces nine separate if checks.
list(beats) gives the keys, ["rock", "paper", "scissors"], and random.choice() picks one of them.
.strip().lower() removes spaces and makes the text lower case, so Paper and paper are accepted.
An unknown move such as lizard prints a message, and continue asks again. round_number does not go up, so the player still gets five real rounds.

Try changing it: more moves

Because the rules are data, a bigger game needs only a bigger dictionary. In rock paper scissors lizard Spock, each move beats two others, so each value is a set:

python

beats = {
    "rock": {"scissors", "lizard"},
    "paper": {"rock", "spock"},
    "scissors": {"paper", "lizard"},
    "lizard": {"spock", "paper"},
    "spock": {"scissors", "rock"},
}


def winner(a, b):
    if a == b:
        return "draw"
    return a if b in beats[a] else b


print(winner("lizard", "spock"))
print(winner("rock", "paper"))
print(winner("spock", "spock"))

output

lizard
paper
draw

Rock paper scissors game in Python

The program

How it works

Try changing it: more moves