PythonHow-ToBeginner · 3 min read

How to Create Abstract Class in Python: Simple Guide

In Python, you create an abstract class by importing ABC and abstractmethod from the abc module and then defining a class that inherits from ABC. You mark methods as abstract using the @abstractmethod decorator, which means subclasses must implement these methods.

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Syntax

To create an abstract class, import ABC and abstractmethod from the abc module. Define a class that inherits from ABC. Use the @abstractmethod decorator to mark methods that must be implemented by subclasses.

ABC: Base class for defining abstract classes.
@abstractmethod: Decorator to declare abstract methods.

python

from abc import ABC, abstractmethod

class MyAbstractClass(ABC):
    @abstractmethod
    def my_method(self):
        pass

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Example

This example shows an abstract class Animal with an abstract method sound. The subclass Dog implements the sound method. Trying to instantiate Animal directly will cause an error.

python

from abc import ABC, abstractmethod

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

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

# dog is an instance of Dog
 dog = Dog()
print(dog.sound())

# animal = Animal()  # This will raise an error

Output

Woof!

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Common Pitfalls

Common mistakes include trying to instantiate an abstract class directly, which raises a TypeError. Also, forgetting to implement all abstract methods in subclasses will cause errors when creating instances.

Always implement every abstract method in subclasses to avoid errors.

python

from abc import ABC, abstractmethod

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

# Wrong: subclass does not implement abstract method
class Car(Vehicle):
    pass

# car = Car()  # Raises TypeError: Can't instantiate abstract class Car with abstract method drive

# Correct implementation
class Bike(Vehicle):
    def drive(self):
        return "Riding the bike"

bike = Bike()
print(bike.drive())

Output

Riding the bike

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Quick Reference

Concept	Description
ABC	Base class to create abstract classes
@abstractmethod	Decorator to mark methods that must be implemented
Cannot instantiate	Abstract classes cannot be instantiated directly
Subclass implementation	Subclasses must implement all abstract methods

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Key Takeaways

Use the abc module's ABC and @abstractmethod to create abstract classes and methods.

Abstract classes cannot be instantiated directly; only subclasses with all abstract methods implemented can be instantiated.

Always implement every abstract method in subclasses to avoid errors.

Abstract classes help define a common interface for subclasses.

Trying to instantiate an abstract class or incomplete subclass raises a TypeError.