with_abc.py

import abc


class Animal(metaclass=abc.ABCMeta):

    @abc.abstractmethod
    def screaming(self):
        'Return when animal screaming the sound hear likes'
        return NotImplemented

    @abc.abstractmethod
    def walk(self, x, y):
        'Make animal walk to position (x, y).'
        return NotImplemented


class Dog(Animal):
    pass


Dog()
"""
TypeError: Can't instantiate abstract class Dog with abstract methods screaming, walk
"""

without_abc.py

class Animal(object):

    def screaming(self):
        'Return when animal screaming the sound hear likes'
        return NotImplemented

    def walk(self, x, y):
        'Make animal walk to position (x, y).'
        return NotImplemented


class Dog(Animal):
    pass


Dog()

"""
Dog not NotImplemented screaming walk method, but can instantiate
"""

python中abc的应用场景

ref
abc — 抽象類別 — 你所不知道的 Python 標準函式庫用法 03