I have the following class where I have defined couple of class variables and a helper class method where I am updating the value of these class variables based on some condition.

class Foo:
    _UPDATED_AT: datetime = datetime.datetime(2000, 1, 1)
    STATUS: bool = False


    @classmethod
    def bar(cls):
        # updated the class variable from here only based on some condition
        if some_cond:
            cls.STATUS = True 
            cls.UPDATED_AT = datetime.datetime.now()

        return cls.STATUS

I want to 1) prevent these class variables from being updated (i.e. being set) directly outside of the class, 2) but to be able to update the classvar from the class method, so semantically something behaving like a private class variable in C++.

I was able to achieve the first of the two requirements by using the a metaclass which basically blocks the attributing setting

class MyMeta(type):
    def __setattr__(cls, key, value):
        raise AttributeError(f"Can't set {cls}.{key}")

However as expected this also prevents updates from happening within the class. I am not sure if this is possible to achieve with pure python but basically I guess somehow I need to detect if the update is happening from inside or outside of the class.

I know we can mark the variables as private in Python with a leading underscore (I already have one in my class) that can tell consumers of your code that these are variables meant for internal use and are not supposed to be used directly by the consumer.

Is this somehow achievable ?