面向对象【七】接口继承

python之接口继承

 

接口继承

接口继承就是（基类）父类定义好2个函数属性（接口），所有的子类必须有这2个函数属性，缺一不可，不是说省代码的，是用来做强制性约束的

基类里面的方法不用具体的实现，只是一个规范而已

1.1实现一个一切皆文件的概念

class Disk:
    def read(self):
        pass
    def write(self):
        pass
class Cdrom:
    def read(self):
        pass
    def write(self):
        pass
class Mem:
    def read(self):
        pass
    def write(self):
        pass

1.2可以定义一个基类，对上面代码进行改进

class Allfile:
    def read(self):
        pass
    def write(self):
        pass
class Disk(Allfile):
    def read(self):
        print("disk read")
    def write(self):
        print("disk write")
class Cdrom(Allfile):
    def read(self):
        print("cdrom read")
    def write(self):
        print("cdrom write")
class Mem(Allfile):
    def read(self):
        print("mem read")
    def write(self):
        print("mem write")

1.3但是子类也可以不按照你规定的出牌，Mem就是不听话，他不定义write的函数属性，然后就会从父类找。父类里面又是pass

class Allfile:
    def read(self):
        pass
    def write(self):
        pass
class Disk(Allfile):
    def read(self):
        print("disk read")
    def write(self):
        print("disk write")
class Cdrom(Allfile):
    def read(self):
        print("cdrom read")
    def write(self):
        print("cdrom write")
class Mem(Allfile):
    def read(self):
        print("mem read")
m1=Mem()
m1.read()
m1.write()

C:\python35\python3.exe D:/pyproject/day25/接口继承.py

mem read

1.4所以python就有一个专门的模块来实现这个强制性的约束子类，模块叫abc

导入模块abc，给父类2个属性加上装饰器之后，如果子类再少属性的话，就直接报错了，这样就强制性的约束了子类必须有父类的2个方法了

import abc
class Allfile(metaclass=abc.ABCMeta):
    @abc.abstractstaticmethod
    def read(self):
        pass
    @abc.abstractstaticmethod
    def write(self):
        pass
class Disk(Allfile):
    def read(self):
        print("disk read")
    def write(self):
        print("disk write")
class Cdrom(Allfile):
    def read(self):
        print("cdrom read")
    def write(self):
        print("cdrom write")
class Mem(Allfile):
    def read(self):
        print("mem read")
m1=Mem()

TypeError: Can't instantiate abstract class Mem with abstract methods write

1.5当子类Mem也加上write这个方法之后就可以正常运行了

import abc
class Allfile(metaclass=abc.ABCMeta):
    @abc.abstractstaticmethod
    def read(self):
        pass
    @abc.abstractstaticmethod
    def write(self):
        pass
class Disk(Allfile):
    def read(self):
        print("disk read")
    def write(self):
        print("disk write")
class Cdrom(Allfile):
    def read(self):
        print("cdrom read")
    def write(self):
        print("cdrom write")
class Mem(Allfile):
    def read(self):
        print("mem read")
    def write(self):
        print("mem write")
m1=Mem()
m1.read()
m1.write()

mem read

mem write