Python set attribute equal to another attribute

Question

Is it possible to have a class attribute targeting another attribute from the same object and have a function to update the value of the target?

class MyObject(object):
    def __init__(self):
        self.var_1 = 1
        self.var_2 = 2
        self.var_3 = 3
        self.current_var = self.var_1

    def update_var(self, value):
        self.current_var = ...

Expected outcome:

>>> x = MyObject()
>>> x.update_var(10)
>>> x.var_1
10
>>> x.current_var = x.var_2
>>> x.update_var(5)
>>> x.var_2
5

Answer 1

You can use the __dict__ of the object or as said by @bla setattr,
And Enum so you don't use string to specify the attribute:

from enum import Enum

class MyObject(object):
    def __init__(self):
        self.var_1 = 1
        self.var_2 = 2
        self.var_3 = 3
        self.current_var = None
    def update_var(self, value):
        if self.current_var is None:
            raise Exception('Current var is not set')
        self.__dict__[self.current_var.name] = value
        setattr(self, self.current_var.name, value) # Same result

m = MyObject()

attrs = vars(m)
attrs_enum = Enum("attrs_enum", attrs)


m.var_1 # 1
m.current_var = attrs_enum.var_1
m.update_var(10)
m.var_1 # 10

m.current_var = attrs_enum.var_2
m.var_2 # 2
m.update_var(20)
m.var_2 # 20

I don't like using a string to specify the attribute, but this is solution