以下代码和运行时错误消息完全说明了问题。
class A():
def __init__(self, x=None):
self._x = x
@property
def x(self):
return self._x
@x.setter
def x(self, x):
self._x = x
# Make two instances of class A
a = A()
b = A()
# Make each instance contain a reference to the other class instance by using
# a setter. Note that the value of the instance variable self._x is None at
# the time that the setter is called.
a.x(b)
b.x(a)
运行时结果:
Traceback (most recent call last):
File "E:\Projects\Commands\Comands\test\commands\test.py", line 19, in <module>
a.x(b)
TypeError: 'NoneType' object is not callable
我正在使用Python 3.7.4运行。
a.x(b)
将:
a.x
-那时是None
None(b)
-由于NoneType
无法调用,这是错误的来源要使用设置器(它是一个描述符),您需要进行属性分配:
a.x = b
b.x = a