What it shows
The computer picks randomly and a dictionary stores what beats what, so the winner is found without a long list of if statements. It shows how data can replace repeated code.
The science
The random.choice function picks one item from a list with equal chance, so over many rounds the computer should win, lose and draw about one third of the time each. The dictionary maps each move to the move it beats, so one lookup decides the winner. Keeping counts of wins in variables lets you test whether the game is fair.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A computer, laptop or phone with a browser (free)
- Python 3 with IDLE, or the free Thonny editor, or an online Python runner (all free)
- A notebook and a pencil
Safety
This project uses safe, everyday materials. Still, read the rules below with a parent before you start.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Create rps.py and write import random, then beats = {"rock": "scissors", "paper": "rock", "scissors": "paper"}.
Set you = 0, bot = 0 and draws = 0, then loop with for round_number in range(10):.
Inside, read your move with move = input("rock, paper or scissors? ").lower() and check it with if move not in beats: print("Invalid"); continue.
Let the computer choose with computer = random.choice(list(beats)) and print("Computer chose", computer).
Decide: if move == computer: print("Draw") and draws += 1.
Add elif beats[move] == computer: print("You win") and you += 1, then else: print("Computer wins") and bot += 1.
After the loop print the three counts and announce the overall winner.
Change the loop to let the computer play itself 3000 times without input and print the percentages to test fairness.
What you should see
The game plays ten rounds and prints who won each. In the 3000 round simulation each outcome comes out near 33 percent, showing that random choice is fair.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What does random.choice do?
It picks one item from a list at random.
2Why use a dictionary for the rules?
One lookup replaces three separate if checks.
3What does continue do?
It skips the rest of the loop and starts the next round.
4Why does the 3000-game test come near one third?
With equal chances, large numbers of trials match the expected probability.
Take it further
Add lizard and Spock with their rules and check by simulation that the game stays fair.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
Computer & office
Computer Fundamentals Study Book
The complete study notes, practice questions and glossary for Computer Fundamentals