abc.md

Abstract Base Classes

If you want to use inheritance but not allow instances of the superclass, you can use the ABC Metaclass. With ABCMeta, you need to create a subclass that overwrites all abstract methods and properties:

:::python3
from abc import ABCMeta, abstractmethod, abstractproperty

class AbstractAnimal(metaclass=ABCMeta):

    @abstractmethod
    def make_noise(self):
        pass

    # an abstract read-only-property
    @abstractproperty
    def species(self):
        pass

    # abstract read/write property
    def getname(self):
        pass

    def setname(self, value):
        pass

    name = abstractproperty(getname, setname)

    # non-abstract method
    def is_alive(self):
        return True

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Exercise

Implement the Dog class so that the code below runs.

:::python3
class Dog(AbstractAnimal):

    ...

rex = Dog()
rex.name = 'Rex'
print(rex.is_alive())
rex.make_noise()
print(rex.species())