抽象类

抽象类

抽象类：本质就是把多个类（People,Dog,Pig），抽取他们比较像的部分，最后得到一个父类（Animal），子类继承父类，让子类在继承的时候必须实现父类规定的一些方法（run、eat）。
具体实现需要借助第三方模块abc。

抽象类本质还是类，只能被继承，不能实例化

好处是：做一种归一化，统一标准，降低使用者的使用复杂度。 

class Animal:
    def run(self):
        pass

    def eat(self):
        pass


class People(Animal):
    def run(self):
        print("people is walking")

    def eat(self):
        print("people is eating")


class Pig(Animal):
    def run(self):
        print("pig is walking")

    def eat(self):
        print("pig is eating")


class Dog(Animal):
    def run(self):
        print("dog is walking")

    def eat(self):
        print("dog is eating")


people = People()
pig = Pig()
dog = Dog()

people.eat()
pig.eat()
dog.eat()

　import abc，@abc.abstractclassmethod后，如果子类不定义@下面的属性，程序就会报错。

import  abc
class Animal(metaclass=abc.ABCMeta):     # 做成抽象类，只能被继承，不能实例化
    @abc.abstractclassmethod      # 只定义规范，不实现具体效果
    def run(self):
        pass

    @abc.abstractclassmethod  # 只定义规范，不实现具体效果
    def eat(self):
        pass


class People(Animal):
    def run(self):
        print("people is walking")


class Pig(Animal):
    def run(self):
        print("pig is walking")

    def eat(self):
        print("pig is eating")


class Dog(Animal):
    def run(self):
        print("dog is walking")

    def eat(self):
        print("dog is eating")


people = People()
# pig = Pig()
# dog = Dog()

# people.eat()
# pig.eat()
# dog.eat()

　TypeError: Can't instantiate abstract class People with abstract methods eat