Py Abstract Classes — Free Python Tutorial

TL;DR: Learn Py Abstract Classes in Python with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.

Py Abstract Classes in Python

An abstract class defines a blueprint that subclasses must implement. Python's abc module provides @abstractmethod decorator — any class with abstract methods cannot be instantiated.

Subclasses that don't implement all abstract methods also become abstract. This enforces a contract: every Shape MUST have area() and perimeter().

Abstract classes can also contain concrete methods (shared logic). Python doesn't have a separate "interface" keyword — abstract classes with only abstract methods serve as interfaces.

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self) -> float: pass    # must override

    def describe(self):              # concrete — shared
        return f"Area = {self.area():.2f}"

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