Python——多态

多态

什么是多态？

多态指的是同一种事物多种形态

为何要用多态？

用基类创建一套规则，强制子类去遵循，这样便可以再不用考虑对象具体类型的前提下而直接使用对象下的方法

如何用多态？

class Animal:
    def eat(self):
        pass
    def drink(self):
        pass
    def bark(self):
        pass
class Cat(Animal):
    def bark(self):
        print('喵喵喵')
class Dog(Animal):
    def bark(self):
        print('汪汪汪')
c = Cat()
d = Dog()

# 可以在不考虑对象具体类型的前提下而直接使用对象下的方法

# 规则强制
import abc #abstract class
class Animal(metaclass=abc.ABCMeta):
    @abc.abstractmethod
    def eat(self):
        pass

    @abc.abstractmethod
    def drink(self):
        pass

    @abc.abstractmethod
    def bark(self):
        pass

# obj=Animal() # 抽象基类本身不能被实例化

class Cat(Animal):
    def eat(self):
        print('cat eat')

    def drink(self):
        print('cat drink')

    def bark(self):
        print('喵喵喵')

class Dog(Animal):
    def eat(self):
        print('dog eat')

    def drink(self):
        print('dog drink')

    def bark(self):
        print('汪汪汪')
def BARK(animal):
    animal.bark()

c = Cat()
c.bark()
BARK(c)

鸭子类型

class Foo:
    def f1(self):
        print('from foo.f1')

    def f2(self):
        print('from foo.f2')

class Bar:
    def f1(self):
        print('from bar.f1')

    def f2(self):
        print('from bar.f2')


obj1=Foo()
obj2=Bar()


obj1.f1()
obj1.f2()

obj2.f1()
obj2.f2()




class Disk:
    def read(self):
        print('disk read')

    def write(self):
        print('disk write')


class Txt:
    def read(self):
        print('txt read')

    def write(self):
        print('txt write')


class Process:
    def read(self):
        print('process read')

    def write(self):
        print('process write')


obj1=Disk()
obj2=Txt()
obj3=Process()


obj1.read()
obj2.read()
obj3.read()