Bulls and Cows

A simple number guessing game built in Python.
The project focuses on clean code structure, testability, and basic QA practices.

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About the project

Bulls and Cows is a classic logic game where the player tries to guess a secret 4-digit number.

Each digit is unique and the number does not start with 0.

After each guess, the player receives feedback:

• Bull → correct digit in the correct position
• Cow → correct digit in the wrong position

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Rules

• The secret number has 4 digits
• All digits are unique
• The number cannot start with 0
• The player must guess the number
• The game ends when the player gets 4 bulls

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Tech stack

• Python 3
• Pytest (unit testing)
• CLI interface

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Project structure

bulls-and-cows/
│
├── src/
│ └── bulls_and_cows/
│     ├── __init__.py
│     ├── generator.py
│     ├── evaluator.py
│     ├── validator.py
│     └── game.py
│
├── tests/
│ ├── test_evaluator.py
│ └── test_validator.py
│
├── cli.py
├── pytest.ini
├── requirements.txt
└── README.md

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How to run the project

Make sure you are in the project root directory.

python -m venv venv

venv\Scripts\Activate.ps1

pip install -r requirements.txt

# On Windows (PowerShell):
$env:PYTHONPATH = "src"; python cli.py

# On Linux/macOS or Git Bash:
PYTHONPATH=src python cli.py

How to run tests

Run all unit tests using:

python -m pytest -v

Example gameplay

• Welcome to Bulls and Cows!

• Try to guess a 4-digit number.

• Enter your guess: 1234

• Result: 1 bull, 2 cows

• Enter your guess: 5678

• Result: 0 bulls, 0 cows

What I learned in this project

• How to structure a Python project using src/ layout
• Writing unit tests with pytest
• Separating logic from input/output (clean architecture basics)
• Debugging real bugs (edge cases with duplicates)
• Working with Git and incremental commits

Possible future improvements

• Web version (Flask / Streamlit)
• Difficulty levels
• Attempt counter / scoring system
• Better UI/UX for CLI
• CI pipeline with GitHub Actions

Author

Patricie Hermanová

Python beginner building projects for QA / junior developer role