Advanced Inheritance

Multiple inheritance, MRO, mixins, and composition patterns.

Overview

Master advanced inheritance patterns.

Multiple Inheritance

class Flying:
    def fly(self):
        return "Flying"

class Swimming:
    def swim(self):
        return "Swimming"

class Duck(Flying, Swimming):
    def quack(self):
        return "Quack"

duck = Duck()
print(duck.fly())   # Flying
print(duck.swim())  # Swimming
print(duck.quack()) # Quack

Method Resolution Order

class A:
    def method(self):
        print("A.method")

class B(A):
    def method(self):
        print("B.method")

class C(A):
    def method(self):
        print("C.method")

class D(B, C):
    pass

d = D()
d.method()  # B.method (MRO: D -> B -> C -> A -> object)
print(D.__mro__)

Mixins

import json

class JSONMixin:
    def to_json(self):
        return json.dumps(self.__dict__)
    
    @classmethod
    def from_json(cls, json_str):
        data = json.loads(json_str)
        return cls(**data)

class User(JSONMixin):
    def __init__(self, name, email):
        self.name = name
        self.email = email

user = User("Alice", "alice@example.com")
json_str = user.to_json()
print(json_str)  # {"name": "Alice", "email": "alice@example.com"}

user2 = User.from_json(json_str)
print(user2.name)  # Alice

Composition

class Engine:
    def __init__(self, horsepower):
        self.horsepower = horsepower
    
    def start(self):
        return "Engine started"

class Car:
    def __init__(self, make, model, horsepower):
        self.make = make
        self.model = model
        self.engine = Engine(horsepower)
    
    def start(self):
        return f"{self.make} {self.model}: {self.engine.start()}"

car = Car("Toyota", "Camry", 200)
print(car.start())  # Toyota Camry: Engine started

Practice

Design a game character system using mixins and composition.