该property()函数返回一个特殊的描述符对象：
>>> property()
<property object at 0x10ff07940>
正是这种对象有额外的方法：
>>> property().getter
<built-in method getter of property object at 0x10ff07998>
>>> property().setter
<built-in method setter of property object at 0x10ff07940>
>>> property().deleter
<built-in method deleter of property object at 0x10ff07998>
>>> property().getter(None)
<property object at 0x10ff079f0>
记住，@decorator语法只是语法糖。语法：
@property
def foo(self): return self._foo
确实与
def foo(self): return self._foo
foo = property(foo)
因此foo该函数被替换property(foo)，我们在上面看到的是一个特殊的对象。然后，当你使用时@foo.setter()，你正在做的事情就是调用property().setter我上面显示的方法，该方法将返回该属性的新副本，但是这次将setter函数替换为装饰方法。
首先，我们property仅使用getter 创建一些函数和一个对象：
>>> def getter(self): print('Get!')
...
>>> def setter(self, value): print('Set to {!r}!'.format(value))
...
>>> def deleter(self): print('Delete!')
...
>>> prop = property(getter)
>>> prop.fget is getter
True
>>> prop.fset is None
True
>>> prop.fdel is None
True
接下来，我们使用该.setter()方法添加setter：
>>> prop = prop.setter(setter)
>>> prop.fget is getter
True
>>> prop.fset is setter
True
>>> prop.fdel is None
True
>>> prop = prop.deleter(deleter)
>>> prop.fget is getter
True
>>> prop.fset is setter
True
>>> prop.fdel is deleter
True
最后但并非最不重要的一点是，该property对象充当描述符对象，因此具有和.__get__()，可以.__set__()与.__delete__()实例属性的获取，设置和删除方法挂钩：
>>> class Foo: pass
...
>>> prop.__get__(Foo(), Foo)
Get!
>>> prop.__set__(Foo(), 'bar')
Set to 'bar'!
>>> prop.__delete__(Foo())
Delete!
Descriptor Howto包括以下类型的纯Python示例实现property()：
class Property:
"Emulate PyProperty_Type() in Objects/descrobject.c"
def __init__(self, fget=None, fset=None, fdel=None, doc=None):
self.fget = fget
self.fset = fset
self.fdel = fdel
if doc is None and fget is not None:
doc = fget.__doc__
self.__doc__ = doc
def __get__(self, obj, objtype=None):
if obj is None:
return self
if self.fget is None:
raise AttributeError("unreadable attribute")
return self.fget(obj)
def __set__(self, obj, value):
if self.fset is None:
raise AttributeError("can't set attribute")
self.fset(obj, value)
def __delete__(self, obj):
if self.fdel is None:
raise AttributeError("can't delete attribute")
self.fdel(obj)
def getter(self, fget):
return type(self)(fget, self.fset, self.fdel, self.__doc__)
def setter(self, fset):
return type(self)(self.fget, fset, self.fdel, self.__doc__)
def deleter(self, fdel):
return type(self)(self.fget, self.fset, fdel, self.__doc__)
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