How to update a variable value if given in kwarg argument? [closed]

I have two classes in a parent-child relation. Variables are assigned values in the parent class and need to be updated in the child class if they are given in the function argument.

class ABC:
    def __init__(self):
        self.var_1 = 'a'
        self.var_2 = 'b'

class XYZ(ABC):
    def __init__(self, **kwargs):
        # what to do here?

Above code is the structure for my project.

Now if I want to update value of any variable, how to do that?

For example, this is how it will work:

>>> a = XYZ()
>>> print(a.var_1)
a

I need it to work like this:

>>> a = XYZ(var_1='updated_value')
>>> print(a.var_1)
updated_value 

Answer

Here is a solution to your problem by accessing the __dict__ of the instance after the __init__ of the superclass:

# Calling the parent ABC is confusing, I thought you were refering to the Abstract Base Class (abc.ABC)
class Parent:
    def __init__(self):
        self.var_1 = 'a'
        self.var_2 = 'b'


class XYZ(Parent):
    def __init__(self, **kwargs):
        super().__init__()
        base_variables = self.__dict__
        for k, v in kwargs.items():
            if k in base_variables:
                self.__setattr__(k, v)


a = XYZ(var_1='updated_value')
print(a.var_1)
>>> updated_value 

Note: by comparing the key with self.__dict__, you make sure that no one can pass random kwargs