Factory class in Python with a mapping dictionary returns TypeError

I made something like this dummy class:

class CreateCaseFactory:
    @classmethod
    def create(cls, user_id: uuid.UUID, type_: str) -> str:
        creator = cls.CASE_TO_METHOD_MAP.get(type_)
        if creator:
            return creator(user_id)
        else:
            raise Exception("Invalid type")

    @classmethod
    def _create_case_1(cls, user_id: uuid.UUID) -> str:
        result = f"Dummy Use Case 1 created for user {user_id}"
        return result

    @classmethod
    def _create_case_2(cls, user_id: uuid.UUID) -> str:
        result = f"Dummy Use Case 2 created for user {user_id}"
        return result

    CASE_TO_METHOD_MAP = {
        "case_1": _create_case_1,
        "case_2": _create_case_2,
    }

but I get an error when I try to run it:

        if creator:
>           return creator(user_id)
E           TypeError: 'classmethod' object is not callable

How can I make this factory class work.

You are trying to call the creator object, which is a class method. In Python, class methods are not directly callable as regular functions.
Example

import uuid


class CreateCaseFactory:

    @classmethod
    def create(cls, user_id: uuid.UUID, type_: str) -> str:
        creator = cls.CASE_TO_METHOD_MAP.get(type_)
        if creator:
            return creator(cls, user_id)  # Call the class method using the class itself
        else:
            raise Exception("Invalid type")

    def _create_case_1(cls, user_id: uuid.UUID) -> str:
        result = f"Dummy Use Case 1 created for user {user_id}"
        return result

    def _create_case_2(cls, user_id: uuid.UUID) -> str:
        result = f"Dummy Use Case 2 created for user {user_id}"
        return result

    CASE_TO_METHOD_MAP = {
        "case_1": _create_case_1,
        "case_2": _create_case_2,
    }


uuid1 = uuid.UUID("12345678-1234-5678-1234-567812345678")
factory = CreateCaseFactory()
case_1 = factory.create(user_id=uuid1, type_="case_1")
print(case_1)
# Dummy Use Case 1 created for user 12345678-1234-5678-1234-567812345678

As the error message says, instances of classmethod are not callable. When you call a class method with something like CreateCaseFactory.create(...), the descriptor protocol "extracts" the underlying function from the class method and calls it with CreateCaseFactory as the first argument.

create_case_1 and _create_case_2 should not be class methods, but regular functions.

class CreateCaseFactory:
    @classmethod
    def create(cls, user_id: uuid.UUID, type_: str) -> str:
        creator = cls.CASE_TO_METHOD_MAP.get(type_)
        if creator:
            return creator(cls, user_id)
        else:
            raise Exception("Invalid type")

    def _create_case_1(cls, user_id: uuid.UUID) -> str:
        result = f"Dummy Use Case 1 created for user {user_id}"
        return result

    def _create_case_2(cls, user_id: uuid.UUID) -> str:
        result = f"Dummy Use Case 2 created for user {user_id}"
        return result

    CASE_TO_METHOD_MAP = {
        "case_1": _create_case_1,
        "case_2": _create_case_2,
    }