Python属性setter如何进行多级设置？

Question

I have created two class A and B (use @property to get and set their attribute). class B has a member whose type is class A. How to set the attribute of bax ?

class A:

class A(object):
    def __init__(self, x=0, y=0):
        self._x = x
        self._y = y

    @property
    def x(self):
        return self._x

    @x.setter
    def x(self, value):
        self._x = value

    @property
    def y(self):
        return self._y

    @y.setter
    def y(self, value):
        self._y = value

class B:

class B(object):
    def __init__(self):
        self._a = A()

    @property
    def a(self):
        return self._a

    @a.setter
    def a(self, value):
        if isinstance(value, A):
            self._a = deepcopy(value)
        elif isinstance(value, tuple):
            self._a = A(value[0], value[1])
        elif isinstance(value, int):
            # ?           
            pass

b = B()
b.a.x = 1 # How to implementate this ?

Am I wrong with the using of @property ?

Answer 1

Your code works fine but if you are looking for another approach you could inherit the A class and bax becomes bx .

You can achieve this by adding the following line in B 's constructor

super(A, self).__init__()

hence bax == bx

Answer 2

adding print() to your classes shows the behaviour, calling bax = 1 will make x.setter in A class in charge not a.setter in B class

example:

class A(object)
    .
    .
    @x.setter
    def x(self, value):
        print('x.setter acting')
        self._x = value


class B(object):
    .
    .
    @a.setter
    def a(self, value):
        print('a.setter acting')  # adding print 
        if isinstance(value, A):
            self._a = deepcopy(value)
        elif isinstance(value, tuple):
            self._a = A(value[0], value[1])
        elif isinstance(value, int):
            # ?           
            pass

b = B()
b.a.x = 1 # x.setter will be in charge not a.setter

output:

x.setter acting

if you want a.setter to be in charge you can:

class B(object):
        .
        .
        @a.setter
        def a(self, value):
            print('a.setter acting')  # adding print 
            if isinstance(value, A):
                self._a = deepcopy(value)
            elif isinstance(value, tuple):
                self._a = A(value[0], value[1])
            elif isinstance(value, int):
                # ?           
                self._a.x = value

b = B()
b.a = 1 # a.setter will be in charge

output:

a.setter acting