Comment by LtWorf

With Literal you can also do this:

    @dataclass
    class Message:
        event: Literal['message']
        msg: str
    
    @dataclass
    class File:
        event: Literal['file']
        url: str
    
    typedload.load(data, File | Message)

Where data is something like `{'event': 'message', 'msg': 'bla'}`.

After the load, you can trust that your objects are well formed and let mypy do its thing.

So types can be useful at runtime as well. Otherwise the alternative would be to use raw dictionary, which mypy can't check.

pydantic does a similar thing but it uses its own different typing, so it needs a mypy plugin or it flags everything as wrong.