Is the Inheritance & super() lesson free?

Yes. The first 5 lessons on PyRun are free forever — no signup, no card. Inheritance & super() runs real Python in your browser via Pyodide.

How long does the Inheritance & super() lesson take?

About 8 minutes end-to-end. It's a hands-on lesson — you read a paragraph, edit the code, and run it in the same tab.

Do I need to install Python to try the Inheritance & super() lesson?

No install required. PyRun runs real CPython in your browser via Pyodide (Python compiled to WebAssembly). Works on Chrome, Firefox, Safari, and Edge — desktop or mobile.

What level is the Inheritance & super() lesson?

Advanced level. Assumes comfort with classes, functions, and standard library. Not for first-time Python learners.

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Advanced·8 min·advanced · oop

Inheritance & super()

You’ll be able to

Extend a base class with a subclass
Override methods while preserving behavior with super()
Understand the is-a relationship inheritance encodes
Decide when composition beats inheritance

Why this matters

Django's class-based views, DRF serializers, and SQLAlchemy's declarative base all lean on multiple inheritance and cooperative super() calls. Understanding the C3 linearization MRO is what separates engineers who can debug a diamond-shaped mixin stack from those who cargo-cult super().__init__() and pray.

Common pitfalls

Forgetting **kwargs in cooperative __init__ — every mixin in a chain must forward unknown args or the MRO breaks silently.
Calling Parent.__init__(self) instead of super().__init__() — this skips siblings in the MRO and defeats mixin composition.
Assuming left-to-right resolution — read Cls.__mro__ before debugging; C3 is subtler than it looks.

A child class inherits every attribute and method of its parent. Override what you want to change.

`super()`

Calls the parent's version of a method. Use it inside __init__ to delegate setup, and inside overridden methods to extend behavior.

When to use it

"B is a kind of A" relationships — Puppy is a Dog
Sharing logic across closely-related types

When NOT to

Just to share helper code → use composition or a module function
More than 2–3 levels deep → usually a smell

Try it

Add a Cat class with its own speak().
Build a Pet mixin that adds owner to any Animal subclass.

Practice

3 graded exercises

Write the code, click Check. We’ll tell you exactly what to fix.

Progress0 / 3

Exercise 1
Given the parent Animal class (already defined below), create a subclass Dog that overrides speak(self) to return "Woof!". Then print Dog("Rex").speak() — expected: Woof!.
Exercise 2
Extend Dog further into a subclass Puppy whose __init__(self, name, breed) uses super().__init__(name) and stores breed. Its speak(self) returns "Yip! Woof!" (uses super().speak()). Print Puppy("Toby", "Lab").speak().
Exercise 3
Given a Shape class with area(self) returning 0, define Circle(radius) and Square(side) — both inherit from Shape and override area. Print Circle(5).area() (~78.54) and Square(4).area() (16). Use math.pi for the circle.

← PreviousClasses & Objects Next →Magic / Dunder Methods

Inheritance & super()

You’ll be able to

Extend a base class with a subclass
Override methods while preserving behavior with super()
Understand the is-a relationship inheritance encodes
Decide when composition beats inheritance

Why this matters

Common pitfalls

Forgetting **kwargs in cooperative __init__ — every mixin in a chain must forward unknown args or the MRO breaks silently.
Calling Parent.__init__(self) instead of super().__init__() — this skips siblings in the MRO and defeats mixin composition.
Assuming left-to-right resolution — read Cls.__mro__ before debugging; C3 is subtler than it looks.

A child class inherits every attribute and method of its parent. Override what you want to change.

`super()`

Calls the parent's version of a method. Use it inside __init__ to delegate setup, and inside overridden methods to extend behavior.

When to use it

"B is a kind of A" relationships — Puppy is a Dog
Sharing logic across closely-related types

When NOT to

Just to share helper code → use composition or a module function
More than 2–3 levels deep → usually a smell

Try it

Add a Cat class with its own speak().
Build a Pet mixin that adds owner to any Animal subclass.

Practice

3 graded exercises

Write the code, click Check. We’ll tell you exactly what to fix.

Progress0 / 3

Exercise 1
Given the parent Animal class (already defined below), create a subclass Dog that overrides speak(self) to return "Woof!". Then print Dog("Rex").speak() — expected: Woof!.
Exercise 2
Extend Dog further into a subclass Puppy whose __init__(self, name, breed) uses super().__init__(name) and stores breed. Its speak(self) returns "Yip! Woof!" (uses super().speak()). Print Puppy("Toby", "Lab").speak().
Exercise 3
Given a Shape class with area(self) returning 0, define Circle(radius) and Square(side) — both inherit from Shape and override area. Print Circle(5).area() (~78.54) and Square(4).area() (16). Use math.pi for the circle.