day28-python之property

1.property用法

# class Goods:

#     def __init__(self):

#         # 原价

#         self.original_price = 100

#         # 折扣

#         self.discount = 0.8

#

#     @property

#     def price(self):

#         # 实际价格 = 原价 * 折扣

#         new_price = self.original_price * self.discount

#         return new_price

#

#     @price.setter

#     def price(self, value):

#         self.original_price = value

#

#     @price.deleter

#     def price(self):

#         del self.original_price

class Goods:

    def __init__(self):

        self.original_price = 100

        self.discount = 0.8

    @property

    def  price(self):

        new_price = self.original_price * self.discount

        return  new_price

    @price.setter

    def price(self,value):

        self.original_price = value

    @price.deleter

    def price(self):

        del self.original_price

obj = Goods()

print(obj.price)

obj.price = 200

print(obj.price)

del obj.price

print(obj.price)

# obj = Goods()

# print(obj.price)        # 获取商品价格

# obj.price = 200   # 修改商品原价

# print(obj.price)

# del obj.price     # 删除商品原价

# print(obj.price)

2.property补充

# class Foo:

#     @property

#     def AAA(self):

#         print('get的时候运行我啊')

#

#     @AAA.setter

#     def AAA(self,val):

#         print('set的时候运行我啊',val)

#     @AAA.deleter

#     def AAA(self):

#         print('del的时候运行我啊')

# #只有在属性AAA定义property后才能定义AAA.setter,AAA.deleter

# f1=Foo()

# f1.AAA

# f1.AAA='aaa'

# del f1.AAA

# class Foo:

#

#     def get_AAA(self):

#         print('get的时候运行我啊')

#     def set_AAA(self,val):

#         print('set的时候运行我啊',val)

#     def del_AAA(self):

#         print('del的时候运行我啊')

#

#     AAA=property(get_AAA,set_AAA,del_AAA)

# #只有在属性AAA定义property后才能定义AAA.setter,AAA.deleter

# f1=Foo()

# f1.AAA

# f1.AAA='aaa'

# del f1.AAA

3.上下文管理协议

# class Foo:

#     def __init__(self,name):

#         self.name=name

#

#     def __enter__(self):

#         print('执行enter')

#         return self

#

#     def __exit__(self, exc_type, exc_val, exc_tb):

#         print('执行exit')

#         print(exc_type)

#         print(exc_val)

#         print(exc_tb)

#         return True

# with Foo('a.txt') as f:

#     print(f)

#     print(asdfsaasdfasdfasdfasdfasfasdfasdfasdfasdfasfdasfd)  #触发__exit__

#     print(f.name)

#     print('-----------------')

#     print('-----------------')

#     print('-----------------')

#     print('-----------------')

#     print('-----------------')

#     print('-----------------')

#     print('-----------------')

# print('000000000000000000000000000000000000000000000')

with obj as  f:
    '代码块'

1.with obj ----》触发obj.__enter__(),拿到返回值

2.as f----->f=返回值、

3.with obj as f  等同于     f=obj.__enter__()

4.执行代码块
一：没有异常的情况下，整个代码块运行完毕后去触发__exit__,它的三个参数都为None
二：有异常的情况下，从异常出现的位置直接触发__exit__
   a：如果__exit__的返回值为True，代表吞掉了异常
   b：如果__exit__的返回值不为True，代表吐出了异常
   c：__exit__的的运行完毕就代表了整个with语句的执行完毕

#自省
hasattr(obj,'属性') #obj.属性  是否存在
getattr(obj,'属性') #获取obj.属性   不存在则报错
getattr(obj,'属性'，'默认值') #获取obj.属性   不存在不会报错，返回那个默认值
setattr(obj，'属性'，'属性的值') #obj.属性=属性的值
delattr(obj，'属性') #del obj.属性

#__getattr__,__setattr__,__delattr__
obj点的方式去操作属性时触发的方法

__getattr__:obj.属性 不存在时触发
__setattr__:obj.属性=属性的值 时触发
__delattr__:del obj.属性 时触发

#__getitem__,__setitem_,__delitem__
obj[‘属性’]的方式去操作属性时触发的方法

__getitem__:obj['属性'] 时触发
__setitem__:obj['属性']=属性的值 时触发
__delitem__:del obj['属性'] 时触发

#__get__,__set__,__delete__
描述就是一个新式类，这个类至少要实现上述三个方法的一个
class 描述符：
   def __get__（）：
      pass
   def __set__（）：
      pass
   def __delete__（）：
      pass

class 类：
   name=描述符（）

obj=类（）
obj.name #get
obj.name='egon' #set
del obj.name #delete

#__del__:析构方法
垃圾回收时触发
4.元类介绍

# class Foo:

#      pass

#

# f1=Foo() #f1是通过Foo类实例化的对象

#

# print(type(f1))

# print(type(Foo))

#

# class Bar:

#     pass

#

# print(type(Bar))

# class Foo:

#     def __init__(self):

#         pass

# print(Foo)

# print(Foo.__dict__)

#

# def __init__(self,name,age):

#     self.name=name

#     self.age=age

# def test(self):

#     print('=====>')

# FFo=type('FFo',(object,),{'x':1,'__init__':__init__,'test':test})

# print(FFo)

# print(FFo.__dict__)

#

# f1=FFo('alex',18)

# print(f1.name)

# f1.test()

5.利用描述符自定制property

# class Lazyproperty:

#     def __init__(self,func):

#         # print('==========>',func)

#         self.func=func

#     def __get__(self, instance, owner):

#         print('get')

#         # print(instance)

#         # print(owner)

#         if instance is None:

#             return self

#         res=self.func(instance)

#         setattr(instance,self.func.__name__,res)

#         return res

    # def __set__(self, instance, value):

    #     pass

class Lazypropery:

    def __init__(self,func):

        self.func = func

    def __get__(self, instance, owner):

        print('get')

        if instance is None:

            return self

        res = self.func(instance)

        setattr(instance,self.func.__name__,res)

        return res

    def __set__(self, instance, value):

        pass

class Room:

    def __init__(self,name,width,length):

        self.name = name

        self.width = width

        self.length = length

    @Lazypropery

    def area(self):

        return  self.width*self.length

    @property

    def areal(self):

        return  self.width*self.length

print(Room.__dict__)

r1 = Room('厕所',1,1)

print(r1.__dict__)

# class Room:

#     def __init__(self,name,width,length):

#         self.name=name

#         self.width=width

#         self.length=length

#     # @property #area=property(area)

#     @Lazyproperty  #area=Lazypropery(area)

#     def area(self):

#         return self.width * self.length

#     @property  #test=property(test)

#     def area1(self):

#         return  self.width * self.length

# # print(Room.__dict__)

# r1=Room('厕所',1,1)

# print(r1.__dict__)

print(r1.area)

print(Room.__dict__)

#实例调用

# print(r1.area)

# print(Room.__dict__)

#类调用

# print(Room.area)

print(Room.area)

print(r1.test)

print(Room.test)

# print(r1.test)

# print(Room.test)

# print(r1.area1)

# print(r1.area1)

# print(r1.area1)

# print(r1.area1)

print(r1.areal)

print(r1.areal)

print(r1.areal)

print(r1.areal)

print(r1.areal)

print(r1.areal)

# print(r1.area)

# print(r1.__dict__)

#

# print(r1.area)

# print(r1.area)

# print(r1.area)

# print(r1.area)

# print(r1.area)

# print(r1.area)

# print(r1.area)

# print(r1.area)

6.类的装饰器

# def deco(func):

#     print('==========')

#     return func

#

# # @deco       #test=deco(test)

# # def test():

# #     print('test函数运行')

# # test()

#

# @deco #Foo=deco(Foo)

# class Foo:

#     pass

# def deco(obj):

#     print('==========',obj)

#     obj.x=1

#     obj.y=2

#     obj.z=3

#     return obj

# @deco #Foo=deco(Foo)

# class Foo:

#     pass

#

# print(Foo.__dict__)

#一切皆对象

# # @deco #test=deco(test)

# def test():

#     print('test函数')

# test.x=1

# test.y=1

# print(test.__dict__)

7.装饰器修订版

# def Typed(**kwargs):

#     def deco(obj):

#         for key,val in kwargs.items():

#             # obj.key=val

#             setattr(obj,key,val)

#         return obj

#     return deco

def Typed(**kwargs):

    def deco(obj):

        for key,val in kwargs.items():

            setattr(obj,key,val)

        return obj

    return  deco

@Typed(x=1,y=2,z=3)

class Foo:

    pass

print(Foo.__dict__)

@Typed(name='egon')

class Bar:

    pass

print(Bar.name)

# @Typed(x=1,y=2,z=3)   #1.Typed(x=1,y=2,z=3) --->deco   2.@deco---->Foo=deco(Foo)

# class Foo:

#     pass

# print(Foo.__dict__)

# @Typed(name='egon')  #@deco   ---->Bar=deco(Bar)

# class Bar:

#     pass

# print(Bar.name)

8.类的装饰器的应用

# class Typed:

#     def __init__(self,key,expected_type):

#         self.key=key

#         self.expected_type=expected_type

#     def __get__(self, instance, owner):

#         print('get方法')

#         # print('instance参数【%s】' %instance)

#         # print('owner参数【%s】' %owner)

#         return instance.__dict__[self.key]

#     def __set__(self, instance, value):

#         print('set方法')

#         # print('instance参数【%s】' % instance)

#         # print('value参数【%s】' % value)

#         # print('====>',self)

#         if not isinstance(value,self.expected_type):

#             # print('你传入的类型不是字符串，错误')

#             # return

#             raise TypeError('%s 传入的类型不是%s' %(self.key,self.expected_type))

#         instance.__dict__[self.key]=value

#     def __delete__(self, instance):

#         print('delete方法')

#         # print('instance参数【%s】' % instance)

#         instance.__dict__.pop(self.key)

class Typed:

    def __init__(self,key,expected_type):

        self.key = key

        self.expected_type = expected_type

    def __get__(self, instance, owner):

        print('get方法')

        return instance.__dict__[self.key]

    def __set__(self, instance, value):

        print('set方法')

        if not isinstance(value,self.expected_type):

            raise TypeError('%s 传入的类型不是%s'%(self.key,self.expected_type))

        instance.__dict__[self.key]=value

    def __delete__(self, instance):

        print('delete方法')

        instance.__dict__.pop(self.key)

def deco(**kwargs):

    def wrapper(obj):

        for key,val in kwargs.items():

            setattr(obj,key,Typed(key,val))

        return  obj

    return  wrapper

@deco(name=str,age=int)

class People:

    name = 'alex'

    def __init__(self,name,age,salary,gender,heigth):

        self.name = name

        self.age = age

        self.salary = salary

print(People.__dict__)

# def deco(**kwargs): #kwargs={'name':str,'age':int}

#     def wrapper(obj): #obj=People

#         for key,val in kwargs.items():#(('name',str),('age',int))

#             setattr(obj,key,Typed(key,val))

#             # setattr(People,'name',Typed('name',str)) #People.name=Typed('name',str)

#         return obj

#     return wrapper

# @deco(name=str,age=int)  #@wrapper ===>People=wrapper(People)

# class People:

#     name='alex'

#     # name=Typed('name',str)

#     # age=Typed('age',int)

#     def __init__(self,name,age,salary,gender,heigth):

#         self.name=name

#         self.age=age

#         self.salary=salary

# # p1=People('213',13.3,13.3,'x','y')

# print(People.__dict__)

9.自定制classmethod

# class ClassMethod:

#     def __init__(self,func):

#         self.func=func

#     def __get__(self, instance, owner): #类来调用,instance为None,owner为类本身,实例来调用,instance为实例,owner为类本身,

#         def feedback(*args,**kwargs):

#             print('在这里可以加功能啊...')

#             return self.func(owner,*args,**kwargs)

#         return feedback

class ClassMethod:

    def __init__(self,func):

        self.func = func

    def __get__(self, instance, owner):

        def feedback(*args,**kwargs):

            print('在这里可以加功能啊...')

            return  self.func(owner,*args,**kwargs)

        return feedback

class People:

    name = 'linhaifeng'

    @ClassMethod

    def say_hi(cls,msg,x):

        print('你好啊,帅哥%s%s%s'%(cls,msg,x))

# People.say_hi('你那是偷心的贼',10)

# class People:

#     name='linhaifeng'

#     @ClassMethod # say_hi=ClassMethod(say_hi)

#     def say_hi(cls,msg,x):

#         print('你好啊,帅哥 %s %s %s' %(cls.name,msg,x))

#

# People.say_hi('你是那偷心的贼',10)

#

# p1=People()

# p1.say_hi('你是那偷心的贼',10)

p1 = People()

p1.say_hi('你那是',11)

10.自定义制元类

# class MyType(type):

#     def __init__(self,a,b,c):

#         print('元类的构造函数执行')

#         # print(a)

#         # print(b)

#         # print(c)

#     def __call__(self, *args, **kwargs):

#         # print('=-======>')

#         # print(self)

#         # print(args,kwargs)

#         obj=object.__new__(self) #object.__new__(Foo)-->f1

#         self.__init__(obj,*args,**kwargs)  #Foo.__init__(f1,*arg,**kwargs)

#         return obj

# class Foo(metaclass=MyType): #Foo=MyType(Foo,'Foo',(),{})---》__init__

#     def __init__(self,name):

#         self.name=name #f1.name=name

class MyType(type):

    def __init__(self,a,b,c):

        print('元类的构造函数执行')

    def __call__(self, *args, **kwargs):

        obj = object.__new__(self)

        self.__init__(obj,*args,**kwargs)

        return obj

class Foo(metaclass=MyType):

    def __init__(self,name):

        self.name = name

# print(Foo)

# f1 = Foo('alex')

# print(f1)

f1 = Foo('alex')

print(f1)

print(f1.__dict__)

# print(Foo)

# f1=Foo('alex')

# print(f1)

# f1=Foo('alex')

# print(f1)

# print(f1.__dict__)

11.自定义制元类精简版

# class MyType(type):

#     def __init__(self,a,b,c):

#         print('元类的构造函数执行')

#     def __call__(self, *args, **kwargs):

#         obj=object.__new__(self)

#         self.__init__(obj,*args,**kwargs)

#         return obj

# class Foo(metaclass=MyType):

#     def __init__(self,name):

#         self.name=name

# f1=Foo('alex')

class MyType(type):

    def __init__(self,a,b,c):

        print('元类的构造函数执行')

    def __call__(self, *args, **kwargs):

        obj = object.__new__(self)

        self.__init__(obj,*args,**kwargs)

        return obj

class Foo(metaclass=MyType):

    def __init__(self,name):

        self.name = name

f1 = Foo('alex')