sync one instance to another instance of different class in python

Question

I have two classes

class A():
    def __init__(self):
        self.a = 1

class B():
    def __init__(self):
        self.b = 2
        self.A = A()
        self.A.a = self.b

and one class contains the other as an instance (maybe inheritance would be better?). I want some properties, say a, of that A instance to be synced some properties of the containing B instances, say b. So in this example

B_instance = B()
print(B_instance.A.a)
B_instance.b=3
print(B_instance.A.a)

the first print statement gives 2 and the second one I want to give 3. But it gives 2, despite python passing by reference name.

thanks @mkrieger1. What do you mean by that. Maybe a line of code? Like self.b=self.A.a? No you cant meean that — Marlo, Apr 24 '20 at 10:51
See for example https://stackoverflow.com/questions/32968945/how-to-forbid-the-assignment-to-some-attributes-and-update-linked-attributes-of — mkrieger1, Apr 24 '20 at 11:43

score 1 · Answer 1 · answered Apr 24 '20 at 10:59

An example using property. Try this:

class A():
    def __init__(self):
        self.a = 1

class B():
    def __init__(self):
        self.A = A()
        self.b = 2

    def set_b(self, value):
        self._b = value
        self.A.a = self._b
    def get_b(self):
        return self._b
    b = property(get_b, set_b)

B_instance = B()
print(B_instance.A.a)
B_instance.b = 3
print(B_instance.A.a)

Output:

2
3

sync one instance to another instance of different class in python

1 Answers1