abstractmethod

The abstractmethod is a decorator in Python used to define abstract methods within abstract base classes (ABCs). An abstract method is a method that is declared but contains no implementation. It serves as a blueprint for methods that must be created within any child classes built from the abstract class. The abstractmethod decorator is part of the abc module in Python's standard library.

When an abstract method is defined using the abstractmethod decorator, it indicates that any subclass of the abstract class must provide an implementation for that method. If a subclass fails to override the abstract method, attempting to instantiate the subclass will result in a TypeError.

The abstractmethod decorator is typically used in conjunction with the ABC class from the abc module. By inheriting from ABC and using the abstractmethod decorator, a class can be defined as an abstract base class, which cannot be instantiated on its own but can be subclassed. This enforces a contract between the base class and its subclasses, ensuring that certain methods are implemented in any concrete subclass.

Here is an example of how to use the abstractmethod decorator:

```python

from abc import ABC, abstractmethod

class Animal(ABC):

@abstractmethod

def sound(self):

pass

class Dog(Animal):

def sound(self):

return "Bark"

class Cat(Animal):

def sound(self):

return "Meow"

# This will raise a TypeError because Animal is an abstract class

# and cannot be instantiated.

# animal = Animal()

dog = Dog()

print(dog.sound()) # Output: Bark

cat = Cat()

print(cat.sound()) # Output: Meow

```

In this example, the Animal class is an abstract base class with an abstract method sound. The Dog and Cat classes are concrete subclasses that provide implementations for the sound method. Attempting to instantiate the Animal class directly would result in a TypeError, as it is an abstract class.