Python program to implement Rock Paper Scissor game

Rock-Paper-Scissors is a Python project where player selects one of three options: Rock, Paper, or Scissors. The computer simultaneously makes a random selection. The program compares both choices using the game rules and declares the winner. The game can be played repeatedly until the user decides to quit.

Example:

1. User Choice: Rock
Computer Choice: Scissors

Result: User Wins

2. User Choice: Paper
Computer Choice: Paper

Result: Draw

Winning Rules

• Rock defeats Scissors.
• Scissors defeats Paper.
• Paper defeats Rock.
• If both players choose the same option, the round ends in a draw.

In this game, randint() built-in function is used for generating random integer values within the given range.

Algorithm

1. Display the rules of the game.
2. Accept the user's choice.
3. Validate the input and ensure it is within the allowed options.
4. Generate the computer's choice randomly.
5. Compare both choices and determine the winner.
6. Display the result of the round.
7. Ask the user whether they want to play again.
8. Repeat the game until the user chooses to exit.

Implementation

import random

# Display game rules
print("Welcome to Rock-Paper-Scissors!\n")
print("Winning Rules:")
print("Rock vs Paper -> Paper wins")
print("Rock vs Scissors -> Rock wins")
print("Paper vs Scissors -> Scissors wins\n")

choices = ["Rock", "Paper", "Scissors"]

while True:

    print("Choose an option:")
    print("1 - Rock")
    print("2 - Paper")
    print("3 - Scissors")

    # Validate user input
    try:
        choice = int(input("Enter your choice: "))
    except ValueError:
        print("Please enter a valid number.\n")
        continue

    while choice < 1 or choice > 3:
        choice = int(input("Please enter a valid choice (1-3): "))

    # User choice
    user_choice = choices[choice - 1]

    print("\nUser choice is:", user_choice)
    print("Now it's Computer's Turn...")

    # Computer choice
    comp_choice = random.randint(1, 3)
    computer_choice = choices[comp_choice - 1]

    print("Computer choice is:", computer_choice)
    print(user_choice, "vs", computer_choice)

    # Determine winner
    if choice == comp_choice:
        print("<== It's a Tie! ==>")

    elif (
        (choice == 1 and comp_choice == 3) or
        (choice == 2 and comp_choice == 1) or
        (choice == 3 and comp_choice == 2)
    ):
        print("<== User Wins! ==>")

    else:
        print("<== Computer Wins! ==>")

    # Play again
    while True:
        ans = input("\nDo you want to play again? (Y/N): ").lower()

        if ans in ['y', 'n']:
            break

        print("Please enter Y or N.")

    if ans == 'n':
        break

    print()

print("\nThanks for playing!")

Output: 

Winning rules of the game ROCK PAPER SCISSORS are:
Rock vs Paper -> Paper wins
Rock vs Scissors -> Rock wins
Paper vs Scissors -> Scissors wins

Enter your choice
1 - Rock
2 - Paper
3 - Scissors

Enter your choice:
1 - Rock
2 - Paper
3 - Scissors

Enter your choice: 1

User choice is: Rock
Computer choice is: Scissors

<== User wins! ==>

Do you want to play again? (Y/N)
N

Thanks for playing!

Explanation:

• Store Available Choices: A list is used to store the three possible options: Rock, Paper, and Scissors.
• Validate User Input: The program uses try-except and conditional checks to ensure the user enters a valid choice.
• Generate Random Selection: The random.randint() function generates a random choice for the computer.
• Map Numbers to Choices: User and computer selections are converted from numeric values to their corresponding string representations.
• Determine the Winner: Conditional statements compare the selected options and identify the winner or a draw.
• Control Game Execution: A while loop allows multiple rounds to be played until the user chooses to exit the game.