A library demonstrating the 23 Gang of Four design patterns implemented in Python with modern idioms and type hints.

• Factory - Create objects without specifying exact class
• Singleton - Ensure only one instance exists
• Builder - Construct complex objects step by step
• Prototype - Clone objects instead of creating new ones
• Abstract Factory - Create families of related objects

• Strategy - Define interchangeable algorithm families
• Observer - Notify dependents of state changes
• Command - Encapsulate requests as objects
• Chain of Responsibility - Pass requests along handler chain
• Interpreter - Interpret language grammar
• State - Alter behavior when internal state changes
• Template Method - Define algorithm skeleton in base class
• Iterator - Access elements sequentially
• Visitor - Separate algorithms from object structure
• Mediator - Reduce coupling between communicating objects
• Memento - Capture and restore object state

• Decorator - Add responsibilities dynamically
• Adapter - Make incompatible interfaces work together
• Composite - Treat individual and composed objects uniformly
• Facade - Provide simplified interface to complex subsystem
• Proxy - Control access to another object
• Bridge - Decouple abstraction from implementation
• Composition/Inheritance - Demonstrate OOP principles

Full documentation available at: https://sorenwacker.github.io/DesignPatterns/

• Introduction
• Overview
• Design Patterns
• Pattern Selection Guide
• Pattern Comparison Guide
• Practical Examples
• Anti-Patterns
• Quick Reference

# Using uv (recommended)
uv pip install -e .

# Using pip
pip install -e .

Run examples:

python examples/factory_logger.py
python examples/strategy_payment.py

Use in code:

from design_patterns.creational.factory import AnimalFactory
from design_patterns.behavioral.strategy import ShoppingCart, CreditCardPayment

factory = AnimalFactory()
dog = factory.get_animal("dog", "Buddy")

cart = ShoppingCart()
cart.set_payment_strategy(CreditCardPayment("1234-5678"))

Run tests:

pytest

Generate documentation locally:

mkdocs serve

MIT License - see LICENSE.