Project: Rock, paper, scissors

Project: Rock, paper, scissors

• You play rock, paper, scissors against the computer.
• The rules live in functions that return an answer, so each part is easy to test.
• You use functions, return, if with and / or, and string methods.

What you will build

rock, paper or scissors? Rock
The computer chose scissors.
You win!

Step 1: who wins?

• Same move: a draw.
• Rock beats scissors, scissors beats paper, paper beats rock.
• A function can return as soon as it knows the answer. The lines after that return do not run.

Step 2: functions can use functions

• message does not repeat the rules. It calls winner and turns the result into words.
• One rule in one place: if the rules change, you change only winner.

Step 3: check what the player typed

• .strip() removes spaces at both ends; .lower() makes small letters.
• A comparison like move == "rock" is already True or False, so you can return it directly.

Play for real

• random.choice(list) picks one item at random: the computer's move. Run this and play in the input box.

import random

def winner(player, computer):
    if player == computer:
        return "draw"
    if (player == "rock" and computer == "scissors") or (player == "scissors" and computer == "paper") or (player == "paper" and computer == "rock"):
        return "player"
    return "computer"

move = input("rock, paper or scissors? ").strip().lower()
computer = random.choice(["rock", "paper", "scissors"])
print("The computer chose " + computer + ".")
print(winner(move, computer))

Now build it

• Three steps. Press Check answer after each one: the checks call your functions with many moves.