Python Calculator

A simple command-line calculator written in Python. Supports four arithmetic operations with input validation, error handling, and a full pytest test suite.

Features

• Addition, subtraction, multiplication, and division
• Input validation — rejects non-numeric arguments with a clear error
• Division-by-zero protection
• Clean CLI powered by argparse
• Comprehensive test coverage with pytest

Requirements

• Python 3.x

Installation

# Clone the repository
git clone https://github.com/terrymclaughlin/copilot-python-calculator.git
cd copilot-python-calculator

# Create and activate a virtual environment
python -m venv .venv
source .venv/bin/activate   # On Windows: .venv\Scripts\activate

# Install test dependencies
pip install pytest

Usage

python calculator.py <operation> <a> <b>

Operation	Command	Result
Addition	python calculator.py add 5 3	8.0
Subtraction	python calculator.py subtract 10 4	6.0
Multiplication	python calculator.py multiply 3 4	12.0
Division	python calculator.py divide 10 2	5.0

Error cases

# Division by zero
python calculator.py divide 5 0
# Error: Cannot divide by zero

# Invalid input
python calculator.py add foo 3
# error: argument a: invalid float value: 'foo'

Running Tests

# Run all tests
pytest test_calculator.py

# Run with verbose output
pytest -v test_calculator.py

Project Structure

copilot-python-calculator/
├── calculator.py        # Core operations and CLI entry point
├── test_calculator.py   # Pytest test suite
└── .venv/               # Python virtual environment (not committed)