• 类的继承


    1.1

    class Animal:
        def __init__(self,name):
            self._name = name
        def shout(self):
            print('{} shouts'.format(self.__class__.__name__))
        @property
        def name(self):
            return self._name
    class Cat(Animal):
        pass
    cat = Cat('garfield')
    cat.shout()
    cat.name
    #通过继承,猫类不用写代码,直接继承父类的属性和方法
    #Cat类没有定义init初始化函数,所有的都继承自Animal

    1.1.1

    class A:
        def __init__(self):
            self.a1 = 'a1'
            self.__a2 = 'a2'
            print('A init')
    class B(A):
        def __init__(self):
            self.b1 = 'b1'
            print('B init')
    b = B() #A init
    b.__dict__ #{'b1': 'b1'}
    #当子类有自己的init函数时,B类的实例b的字典就只有自己传入的参数,参照1.5父类和子类都有init函数,子类需要调用父类的init函数

    1.2

    class Animal:
        __COUNT = 100
        HEIGHT = 0
        def __init__(self,age,weight,height):
            self.__COUNT += 1
            self.age = age
            self.__weight = weight
            self.HEIGHT = height
        def eat(self):
            print('{} eat'.format(self.__class__.__name__))
        def __getweight(self):
            print(self.__weight)
        @classmethod
        def showcount1(cls):
            print(cls.__COUNT)
        @classmethod
        def __showcount2(cls):
            print(cls.__COUNT)
        def showcount3(self):
            print(self.__COUNT)
    class Cat(Animal):
        NAME = 'CAT'
        __COUNT = 200
    c = Cat(3,5,15)
    c._Animal__getweight()
    Cat.__dict__

    1.3

    class Animal:
        def shout(self):
            print('Animal shouts')
    class Cat(Animal):
        def shout(self):
            print('miao')
        def shout(self):
    #         print(super())
    #         print(super(Cat,self))
            super().shout()
            super(Cat,self).shout()
            self.__class__.__base__.shout(self)
    c = Cat()
    c.shout()
    class Animal:
        def shout(self):
            print('Animal shouts')
    class Cat(Animal):
        def shout(self):
            print('miao')
        def shout(self):
    #         print(super())
    #         print(super(Cat,self))
            super().shout()
            super(Cat,self).shout()
            self.__class__.__base__.shout(self)
    c = Cat()
    c.shout()

    1.4

    class Animal:
        @classmethod
        def class_method(cls):
            print('class_method_animal')
        @staticmethod
        def static_method():
            print('static_method_animal')
    class Cat(Animal):
        @classmethod
        def class_method(cls):
            print('class_method_cat')
        @staticmethod
        def static_method():
            print('static_method_cat')
    c = Cat()
    c.class_method()
    c.static_method()
    #这些方法都可以覆盖,原理都一样,属性字典的搜索顺序

    1.5

    class A:
        def __init__(self,a):
            self.a = a
    class B(A):
        def __init__(self,b,c):
            A.__init__(self,b+c)
            self.b = b
            self.c = c
        def printv(self):
            print(self.b)
            print(self.a)
    #好习惯,父类中定义了init,你就改在子类中的init调用它
    f = B(200,300)
    f.printv()
    f.__dict__
    f.__class__.__bases__

    1.6

    class Animal:
        def __init__(self,age):
            print('animal init')
            self.__age = age
        def show(self):
            print(self.__age)
            
    class Cat(Animal):
        def __init__(self,age,weight):
            super().__init__(age)
            print('cat init')
            self.__age = age +1
            self.__weight = weight
    c = Cat(10,5)
    a = Animal(100)
    c.__dict__ #{'_Animal__age': 10, '_Cat__age': 11, '_Cat__weight': 5}
    a.__dict__ #{'_Animal__age': 100}
    c.show() #10
    #自己的私有属性,就该自己的方法修改,和读取,不要借助其他的类和方法

    1.7

    class Animal:
        def __init__(self,age):
            print('animal init')
            self.age = age
        def show(self):
            print(self.age)
            
    class Cat(Animal):
        def __init__(self,age,weight):
    #         super().__init__(age)
            print('cat init')
            self.age = age +1
            self.weight = weight
    c = Cat(10,5)
    a = Animal(100)
    c.__dict__ #{'age': 11, 'weight': 5}
    a.__dict__ #'age': 100}

     2.1Mixin类

    class Document:
        def __init__(self,content):
            self.content = content
        def print(self):
            raise NotImplementedError()
    class Word(Document):
        pass
    class Pdf(Document):
        pass
    #基类提供的方法不应该具体实现,因为它未必适合子类的打印,子类中需要覆盖重写
    #print是一种能力=====打印能力不是所有的document的子类都需要,所以从这个角度出发有问题
    #2.需要打印的子类加上
    #2.1如果在现有的子类直接加上,违反了ocp原则,继承后增加

    引出了mixin类

    class Document:
        def __init__(self,content):
            self.content = content
    class Word(Document):pass
    class Pdf(Document):pass
    
    class PrintableMinin:
        def print(self):
            print(self.content)
    
    class PrintableWord(PrintableMinin,Word):pass
    print(PrintableWord.__dict__)
    print(PrintableWord.__mro__)
    p = PrintableWord('abc')
    p.print()
    使用原则:
    mixin类中不应该显示的出现init初始化方法
    通常不能独立工作,因为他是准备混入别的类中的
    mixin的类的祖先也应该是mixin类
    本文为原创文章,转载请标明出处
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  • 原文地址:https://www.cnblogs.com/harden13/p/9010757.html
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