Hi, thanks for featuring my result library!

Regarding your criticism that `result.ok()` returns `None` if the value is not an `Ok` type: That's what `result.unwrap()` and `result.expect(msg)` are for :) (There's no unwrap_err and expect_err so far, but PRs are welcome.) The lib is strongly inspired by Rust (see https://doc.rust-lang.org/std/result/enum.Result.html), that's why `result.ok()` returns something option-ish.

I like your `isinstance` approach btw! Will have to think about it a bit more. Reminds me a bit of Typescript as well. Does mypy have type guards (https://www.typescriptlang.org/docs/handbook/advanced-types....)? Maybe that could be used to create helper functions that check for success/failure and which help mypy to derive the correct type.

Thanks for writing it! I'm a Python programmer in my day job. I have sometimes remarked that the reason I play around with Haskell in my free time is because I don't want to see another run time type error unless I'm being paid to do so. But I needed to do some spreadsheet-scraping and data-munging for a personal project and I figured it would be easier in Python. So I searched and found your article and it was just what I needed.

Now to sneak it in at work...

I’ve written a similar python library called `safetywrap` that implements both Result and Option types from rust, with almost all of the interfaces implemented, including unwrap, map, flat map, err_map, etc. It fully supports types and works well with mypy.

Feel free to give it a shot! https://pypi.org/project/safetywrap/