How to Use Abstract Classes in Python

An abstract class is a class that cannot be instantiated directly. Its main purpose is to be inherited by other classes that implement the methods defined as abstract in the base class.

In Python, abstract classes are implemented using the abc (Abstract Base Classes) module. This module provides tools for defining abstract classes and methods.

from abc import ABC, abstractmethod

Defining an Abstract Class

To define an abstract class, it must inherit from ABC and use the @abstractmethod decorator to mark the methods that must be implemented by subclasses.

from abc import ABC, abstractmethod

class Animal(ABC):
    @abstractmethod
    def make_sound(self):
        pass

    def sleep(self):
        print("The animal is sleeping.")

Implementing Derived Classes

Classes that inherit from an abstract class must implement all abstract methods. If a subclass does not implement an abstract method, it also becomes an abstract class and cannot be instantiated.

Let’s see how to implement our abstract class Animal

class Dog(Animal):
    def make_sound(self):
        print("The dog barks.")

class Cat(Animal):
    def make_sound(self):
        print("The cat meows.")

Mixed Classes

An abstract class can have both abstract methods and concrete methods. Concrete methods provide a default implementation that can be inherited or overridden by subclasses.

Let’s see it with an example,

class Vehicle(ABC):
    @abstractmethod
    def drive(self):
        pass

    def start(self):
        print("The vehicle is started.")

class Car(Vehicle):
    def drive(self):
        print("The car is driving.")

class Motorcycle(Vehicle):
    def drive(self):
        print("The motorcycle is driving.")