class C(object):
    def getx(self): 
        return self._x
    
    def setx(self, value): 
        self._x = value
        
    def delx(self): 
        del self._x
    
    x = property(getx, setx, delx, "I'm the 'x' property.")

property類結(jié)合x = property(getx, setx, delx, "I'm the 'x' property.")與property的__init__()可以發(fā)現(xiàn)property接受四個(gè)參數(shù)

fget，用于獲取屬性值，

fset，用于設(shè)置屬性值

fdel，用于刪除屬性

doc，屬性的介紹

可以單獨(dú)設(shè)置fget、fset、fdel…

x = property，x.getter(getx)，x.setter(setx)，x.deleter(delx)

class property(object):
    
    def deleter(self, *args, **kwargs): # real signature unknown
        """ Descriptor to change the deleter on a property. """
        pass

    def getter(self, *args, **kwargs): # real signature unknown
        """ Descriptor to change the getter on a property. """
        pass

    def setter(self, *args, **kwargs): # real signature unknown
        """ Descriptor to change the setter on a property. """
        pass

    def __delete__(self, *args, **kwargs): # real signature unknown
        """ Delete an attribute of instance. """
        pass

    def __getattribute__(self, *args, **kwargs): # real signature unknown
        """ Return getattr(self, name). """
        pass

    def __get__(self, *args, **kwargs): # real signature unknown
        """ Return an attribute of instance, which is of type owner. """
        pass

    def __init__(self, fget=None, fset=None, fdel=None, doc=None): # known special case of 
        pass

使用裝飾器的聲明方式

需要注意，裝飾器只是一個(gè)python的語(yǔ)法糖，可以拆解成普通使用方法，如property(getx)

@property創(chuàng)建了一個(gè)實(shí)例x，對(duì)于def x(self)實(shí)際上是C類持有x = property(fget=x)

因此，x.setter方法指向的是property.setter，也是起到裝飾器效果x.setter(x)（注意，前者x是property實(shí)例x，后者x是def x(self, value)函數(shù)），x.deleter同理

class C(object):
    @property
    def x(self):
        "I am the 'x' property."
        return self._x
    
    @x.setter
    def x(self, value):
        self._x = value
        
    @x.deleter
    def x(self):
        del self._x

為什么property實(shí)例化后的名字與屬性名一致？

換種問(wèn)法就是為什么x = property(...)

可以認(rèn)為是

attributes_and_methods = {
    x.__name__: property(x), //聲明C類持有property實(shí)例
    #...
}
C = type('C', (object,), attributes_and_methods)

使用裝飾器的調(diào)用過(guò)程

執(zhí)行C().x時(shí)，調(diào)用的是C().x（property）綁定的fget方法，用過(guò)__get__喚醒，setter、deleter同理

class property(object):
    
    #...
    def __init__(self, fget=None, fset=None, fdel=None, doc=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel
        ...

    def __get__(self, obj, objtype=None): # real signature unknown
        if obj is None:
            return self
        if self.fget is None:
            raise AttributeError("unreadable attribute")
        return self.fget(obj)