Inheritance & MRO

Introduction

Python supports multiple inheritance with C3-linearized MRO (Method Resolution Order). Prefer composition; use inheritance for true is-a relationships.

Understanding the topic

Core concepts to understand:

• class Dog(Animal): — subclass.
• super().__init__() calls parent.
• Cls.__mro__ shows resolution order.
• isinstance and issubclass.

Syntax reference

Visual flow / code:

class Animal:
    def __init__(self, name): self.name = name
    def speak(self): return "..."

class Dog(Animal):
    def speak(self): return "Woof!"

class Puppy(Dog):
    def speak(self):
        return super().speak() + " (yip!)"

p = Puppy("Rex")
print(p.speak())                 # 'Woof! (yip!)'
print(Puppy.__mro__)             # MRO chain

Execution workflow

Real-world use

Mixins are a common Python pattern: small classes that add specific behavior (e.g., SerializableMixin, LoggingMixin).

Best practices

• Prefer composition over inheritance.
• Use mixins for cross-cutting behavior.
• Always call super().__init__.

Common mistakes

• Deep hierarchies → diamond problem; MRO solves it but hierarchies should still stay shallow.

Hands-on exercise

Interview preparation — practice these questions:

• What's MRO?
• Composition vs inheritance?
• What are mixins?

Summary

In summary: super() + MRO handle multi-inherit. Composition usually wins.