The Python example feels like a strawman. You can write Python in a way that gets you most of the benefits of the Haskell version if you wanted to: @datacl

The Python example feels like a strawman. You can write Python in a way that gets you most of the benefits of the Haskell version if you wanted to: @dataclass class InvalidResultError: result: str def do_something() -> int | InvalidResultError: result = get_result() return 42 if result == "a result" else InvalidResultError(result) Using a dataclass like this seems a little overkill, but it does get you something close to `Either`. I also don't understand the argument against nullable types: you could return `int | None` here, which would be the same as treating a `Maybe` (you have to explicitly consider the case where there is no value)