Example code from Head First Design Patterns second edition translated to python to help me understand and memorise the patterns.

I have added examples of pattern usage in the Python standard library and pypi - I am starting to see patterns everywhere!

Note I am aiming for a mostly literal translation whilst trying to make the code a little more pythonic by, e.g. using python conventions for ClassNames and method_names and putting all of the code in a single file where it makes sense to do so.

• Strategy
• Observer
• Decorator
• Factory Method
• Simple Factory
• Abstract Factory
• Builder(Bonus Pattern)
• Singleton
• Command
• Adapter
• Façade
• Template Method
• Iterator
• Composite
• State
• Proxy
• Model View Controller (MVC)
• Manager(Bonus Pattern)
• Result(Bonus Pattern)

From the book 📖:

packageheadfirst.designpatterns.strategy; publicabstractclassDuck { FlyBehaviorflyBehavior; QuackBehaviorquackBehavior; publicDuck() { } publicvoidsetFlyBehavior(FlyBehaviorfb) { flyBehavior = fb; } publicvoidsetQuackBehavior(QuackBehaviorqb) { quackBehavior = qb; } abstractvoiddisplay(); publicvoidperformFly() { flyBehavior.fly(); } publicvoidperformQuack() { quackBehavior.quack(); } publicvoidswim() { System.out.println("All ducks float, even decoys!"); } }

From this repository :

classDuck(): _fly_behavior=None_quack_behavior=Nonedefset_fly_behavior(self, fly_behavior): self._fly_behavior=fly_behaviordefset_quack_behavior(self, quack_behavior): self._quack_behavior=quack_behaviordefdisplay(self): raiseNotImplementedErrordefperform_fly(self): self._fly_behavior.fly() defperform_quack(self): self._quack_behavior.quack() defswim(self): print("All ducks float, even decoys! 〰🦆〰")

• Encapsulate what varies
• Open-Closed Principle: Open for extension, closed for modification
• Program to an interface, not to an implementation
• Favour composition over inheritence
• Dependency Inversion Principle
• Depend upon abstractions
• The Hollywood Principle : "Don't call us, we'll call you"
• One Class, One Responsibility Principle
• Single Responsibility Principle
• Principle of Least Knowledge

I started to work on the MVC pattern here but have a small complete MVC implementation in JavaScript in another repo.