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