python类的私有属性

1. 限制属性
   只能初始化这些规定的属性，不能添加别的属性

   class Exployee:
       __slots__=['id','age','name']
       def __init__(self,id,age):
           self.id=id
           self.age=age
       def __str__(self):
           retrun self.id
   ex=Exployee('001',20)
   ex.name='tom'
   print(ex)

2. 私有属性
   变量名以双下划线开头，只能在类内部访问，可以采用共有方法访问私有属性

   class Exployee:
       nation='china'
       def __init__(self,id,age):
           self.__id=id
           self.__age=age
       def getId(self):
           return self.__id#只读
       def setId(self,id):
           self.__id=id#只写
   ex01=Exployee('001',20)
   print(ex01.getId())#得到id
   ex01.setId('008')#改变id
   print(ex01.getId())

3. @property

   class Exployee:
       def __init__(self,id,age)
           self.__id=id
           self.__age=age
       @property
       def age(self):
           return self.__age
       @age.setter
       def age(self,myage):
           self.__age=myage
   
       ex01=Exployee('001',20)
       print(ex01.age)
       ex01.age=22
       print(ex01.age)

4. 类方法

   class Exployee:
       nation='china'
       __acount=0
       def __init__(self,id):
           self.__id=id
           Exployee.__acount+=1
       def __del__(self):#删除
           Exployee.__acount-=1
       @classmethod
       def show(cls):
           return cls.nation
       @classmethod
       def acount(cls):
           return cls.__acount
       @staticmethod
       def display():
           print('i am Exployee')
   ex1=Exployee('001')
   ex2=Exployee('001')
   ex3=Exployee('001')
   del ex1#删除ex1
   print(Exployee.acount)#输出2