ABC List in Python

In Python, we can use the abc module to create abstract base classes (ABCs). An ABC is a class that cannot be instantiated, and serves as a blueprint for concrete classes to inherit from. Using ABCs allows us to define common interfaces that concrete classes must implement, which helps to ensure that our code is well-designed and maintainable.

To create an ABC, we need to import the ABC class from the abc module:

from abc import ABC

We can then create our own custom ABC by subclassing ABC:

class MyABC(ABC):
    pass

This class doesn't do anything on its own, but it can be used as a base class for other classes that need to implement its interface. To do this, we use the @abstractmethod decorator to mark methods that must be implemented:

from abc import ABC, abstractmethod

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

Here, we have defined an abstract method my_method that must be implemented by any concrete class that inherits from MyABC. If a concrete class does not implement this method, attempting to instantiate it will raise a TypeError.

We can also use the register method of an ABC to register a class as implementing its interface:

from abc import ABC, abstractmethod

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

class MyConcreteClass:
    def my_method(self):
        print('Hello, world!')

MyABC.register(MyConcreteClass)

Now, MyConcreteClass is considered to be a subclass of MyABC, even though it doesn't inherit directly from it. This allows us to use it seamlessly with any code that expects an instance of MyABC.

In summary, the abc module in Python allows us to define abstract base classes that define a common interface for concrete classes to implement. Using ABCs makes our code more maintainable and ensures that it is well-designed.