ABC

Learn abstract classes with abc.ABC.

Abstract class (ABC)

An abstract class is a class that you do not instantiate directly and that acts as a template for subclasses. In Python you define it by inheriting from the ABC class in the abc module.

Example: from abc import ABC\nclass Animal(ABC):\n pass. Here Animal is now an abstract class. If you try to create an instance with Animal() you get a TypeError; but you can subclass it and instantiate the subclass. Abstract classes enforce a shared interface.

Inheriting from ABC

The shortest way to define an abstract class is to inherit from ABC. Even if you put no abstract methods in the body, ABC inheritance blocks any attempt to instantiate. This signals “this class should not be used alone”.

An abstract class gives subclasses a common behavior frame. A subclass inherits the abstract class and fills in the missing methods. So different subclasses conform to the same interface; the caller does not need to know which subclass it is.

Exercise Define the abstract class

Start with from abc import ABC. Define an abstract class Animal(ABC); its body should be pass. Then print the abstract base relation with print(issubclass(Animal, ABC)).

Show example solution

# Import ABC from abc and define the Animal abstract class
from abc import ABC

class Animal(ABC):
    pass

print(issubclass(Animal, ABC))

Test yourself

What happens after defining Animal(ABC)?
- Animal() returns a new instance
- Animal() raises TypeError
- Animal automatically becomes a subclass
- Animal is ignored
Show answer

Animal() raises TypeError — An abstract class cannot be instantiated directly; it raises TypeError.

Complete the import line

from ____ import ABC

class Animal(ABC):
    pass

Show answer

from abc import ABC

class Animal(ABC):
    pass

Match the ABC parts

abc

Module
ABC

Base class
class Animal(ABC)

Abstract definition
TypeError

Instantiation error

Next lesson: @abstractmethod

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