python中property简单使用与实现

property简单使用

 class P:
     """
         property简单使用
     """
     def __init__(self,name):
         self._name = name

     @property
     def name(self):
         return self._name

     @name.setter
     def name(self,val):
         self._name = val

     @name.deleter
     def name(self):
         del self._name

 p = P("zhangsan")
 print(p.name)
 print(p.__dict__)
 p.name = "wangsi"
 print(p.name)
 print(p.__dict__)

结果：

 zhangsan
 {'_name': 'zhangsan'}
 wangsi
 {'_name': 'wangsi'}

property简单实现

 class Property:

     def __init__(self,fget=None,fset=None,fdel=None):
         self.fget = fget
         self.fset = fset
         self.fdel = fdel
         pass

     def __set__(self, instance, value):
         self.fset(instance,value)
         return self

     def __get__(self, instance, owner):
         if not instance:
             return self
         return self.fget(instance)

     def __delete__(self, instance):
         self.fdel(instance)
         return self

     def setter(self,fn):
         #保留设置函数的副本
         self.fset = fn
         return self

     def deleter(self,fn):
         # 保留删除函数的副本
         self.fdel = fn
         return self

 class Person:

     # d = Property()
     def __init__(self,data):
         self._data = data

     @Property   #等价式  data=Propery(data)
     def data(self):
         return self._data

     @data.setter   #等价式  data=data.setter(data)
     def data(self,val):
         self._data = val

     @data.deleter  #等价式  data=data.deleter(data)
     def data(self):
         del self._data

 p = Person(19)
 p.data = 123
 print(Person.__dict__)
 print(p.__dict__)
 del p.data
 print(Person.__dict__)
 print(p.__dict__)

结果：

 {'__init__': <function Person.__init__ at 0x0000015F3F0F0598>, '__dict__': <attribute '__dict__' of 'Person' objects>, 'data': <__main__.Property object at 0x0000015F3F0FE240>, '__weakref__': <attribute '__weakref__' of 'Person' objects>, '__module__': '__main__', '__doc__': None}
 {'_data': 123}
 {'__init__': <function Person.__init__ at 0x0000015F3F0F0598>, '__dict__': <attribute '__dict__' of 'Person' objects>, 'data': <__main__.Property object at 0x0000015F3F0FE240>, '__weakref__': <attribute '__weakref__' of 'Person' objects>, '__module__': '__main__', '__doc__': None}
 {}

注意：property 依赖装饰器和数据描述器实现

　　数据描述器：需要实现__set__()方法和__get__()方法

　　非数据描述器：需实现__get__()方法