Abstract Class

Abstract Base Classes are classes that are only meant to be inherited from and won't allow to create instance. In Python, abstract class can be created using abc module. The following examples shows creation of abstract class using abc module.

from abc import ABCMeta

class Bar:
    __metaclass__ = ABCMeta

    @abstractmethod
    def my_abstract_method(self):
        return

    @abstractproperty
    def my_abstract_property(self):
        return

class Foo(Bar):

    def my_abstract_method(self):
        return 

    def my_abstract_property(self):
        return

Bar.register(SomeRandomClass) 

Setting a class's metaclass to ABCMeta and making one of its methods virtual makes it an ABC. A virtual method is one that the ABC says must exist in child classes, but doesn't necessarily actually implement.

There are two ways to indicate that a concrete class implements an abstract: register the class with the abstract base class or subclass directly from the abstract base class. I have done both in above example.

abstractmethod:
A decorator indicating abstract methods. A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract methods and properties are overridden. The abstractmethod() only affects subclasses derived using regular inheritance; “virtual subclasses” registered with the ABC’s register() method are not affected.

abstractproperty:
A subclass of the built-in property(), indicating an abstract property.

Note: In python, the abstract methods can have implementation. This implementation can be called via the super() mechanism from the class that overrides it. The abstract property declared above is the read only. To define read-write abstract property, refer python official documentation.