Shared via mypy Playground

main.py

from typing import Protocol, TypeVar


class Type1:
    data1 = 1

    def method1(self) -> None:
        print(self.data1)


class Type2:
    data2 = 2

    def method2(self) -> None:
        print(self.data2)


PossibleBaseClass = type[Type1 | Type2]
BaseClassT = TypeVar("BaseClassT", bound=PossibleBaseClass)


class ExampleT(Protocol[BaseClassT]):
    base_class: type[BaseClassT]


class Example(ExampleT[BaseClassT]):
    def __new__(
            cls,
            base_class: type[BaseClassT],
    ) -> BaseClassT:
        new_class = type(
            cls.__name__,
            (cls, *base_class.__mro__),
            {**cls.__dict__, **base_class.__dict__},
        )
        result = super(base_class, new_class).__new__(new_class)
        result.base_class = base_class
        return result

    def method(self) -> None:
        if self.base_class is Type1:
            return self.method1()
        if self.base_class is Type2:
            return self.method2()
        raise NotImplementedError


class ExampleSubclass(Example):
    def upper_level_logic(self) -> None:
        print("header")
        self.method()


ExampleSubclass(base_class=Type1).upper_level_logic()
ExampleSubclass(base_class=Type2).upper_level_logic()