Build Rock Paper Scissors in Python

A duel against the computer

Rock Paper Scissors is the perfect second Python project. The rules are tiny — rock beats scissors, scissors beat paper, paper beats rock — but coding them teaches you how to compare values, make decisions, and keep score. By the end you'll have a game you can play against the computer as many times as you like.

If you can already use making decisions with if, you're ready. Let's build it up step by step.

Step 1: let the computer choose

The computer needs to pick rock, paper or scissors at random. random.choice grabs one item from a list:

import random

choices = ["rock", "paper", "scissors"]
computer = random.choice(choices)

Now computer holds one of the three moves, chosen fairly each time. (More on this in random numbers and games in Python.)

Step 2: get the player's move

We read the player's move with input() and use .lower() so capital letters don't matter:

player = input("rock, paper or scissors? ").lower()

If they type Rock, .lower() turns it into rock, matching our list.

Step 3: decide who wins

This is the heart of the game. First check for a tie. Then list the three ways the player wins. Everything else is a loss:

if player == computer:
    print("It's a tie!")
elif (player == "rock" and computer == "scissors") or \
     (player == "paper" and computer == "rock") or \
     (player == "scissors" and computer == "paper"):
    print("You win!")
else:
    print("Computer wins!")

There are only three winning combinations, so we can write them all out. The \ at the end of a line just lets one long condition continue onto the next line for readability. (For more on and/or, see python comparison and logic.)

The complete game

Here it is all together, with score keeping and a play-again loop:

import random

choices = ["rock", "paper", "scissors"]
player_score = 0
computer_score = 0

print("=== ROCK PAPER SCISSORS ===")

while True:
    player = input("\nrock, paper or scissors? ").lower()

    if player not in choices:
        print("Please type rock, paper or scissors.")
        continue

    computer = random.choice(choices)
    print(f"Computer chose {computer}.")

    if player == computer:
        print("It's a tie!")
    elif (player == "rock" and computer == "scissors") or \
         (player == "paper" and computer == "rock") or \
         (player == "scissors" and computer == "paper"):
        print("You win this round!")
        player_score += 1
    else:
        print("Computer wins this round!")
        computer_score += 1

    print(f"Score — You: {player_score}  Computer: {computer_score}")

    again = input("Play again? (yes/no): ").lower()
    if again != "yes":
        print("Final score — You:", player_score, "Computer:", computer_score)
        print("Thanks for playing!")
        break

How the new parts work:

1. player not in choices checks the move is valid. If not, continue skips to the top of the loop and asks again.
2. player_score += 1 adds one to the winner's total. The scores survive between rounds because they live outside the loop.
3. The \n inside the print adds a blank line so each round is easy to read.

A sample game:

=== ROCK PAPER SCISSORS ===

rock, paper or scissors? rock
Computer chose scissors.
You win this round!
Score — You: 1  Computer: 0
Play again? (yes/no): yes

rock, paper or scissors? paper
Computer chose scissors.
Computer wins this round!
Score — You: 1  Computer: 1
Play again? (yes/no): no
Final score — You: 1 Computer: 1
Thanks for playing!

Why list the wins, not the losses?

Notice we only spelled out the three ways the player wins, then let else cover every loss. That's a neat pattern: when one outcome has fewer cases than the other, check the short list and let else mop up the rest. It keeps your code shorter and easier to read.

Try it yourself

Make the game your own:

• Best of five. Stop the game automatically when someone reaches 3 wins. Use the while loop condition while player_score < 3 and computer_score < 3:.
• Add emojis. Print ✊ for rock, ✋ for paper and ✌️ for scissors using a small dictionary that maps each move to its emoji.
• Lizard and Spock. Add "lizard" and "spock" to the choices and extend the win rules. Each move now beats two others.
• Track ties. Add a ties counter and report it at the end alongside the wins.