metaclasses_pseudo_private.py

class Desc:
    def __set_name__(self, owner, name):
        self.field_name = name
    def __get__(self, instance, *args):
        if self.field_name in instance.__dict__.keys():
            return instance.__dict__[self.field_name]
        else:
            return "NoneDescriptor"
    def __set__(self, instance, value, *args):
        instance.__dict__[self.field_name] = value

class Meta(type):
    # HERE HERE HERE
    cnt: int = 0
    def __new__(cls, *args):
        # HERE HERE HERE
        args[2]['_{}__id'.format(cls.__name__)] = Meta.cnt
        rv = super().__new__(cls, *args)
        assert(
            '_Meta__id' in rv.__dict__.keys()
        )
        Meta.cnt = Meta.cnt + 1
        return rv
    def __init__(self, *args):
        super().__init__(*args)
    def __call__(self, *args):
        return super().__call__(*args)

class Type(metaclass=Meta):
    foo = Desc()
    bar = Desc()

b = Type()
print(b.foo)
b.foo = "ff"
print(b.foo)