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Hi, I'm the author! Happy to answer your questions here!

dbrgn 7y ago
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 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.html#type-guards-and-differentiating-types 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.
- uryga 7y ago
  > Does mypy have type guards? not yet, maybe in the future. might be possible to emulate some use cases with Literal Types. tracking issue: https://github.com/python/mypy/issues/5206 https://github.com/python/mypy/issues/5206
- karlicoss 7y ago
  Oh, not sure how I missed these methods, thanks! I'll update the post to reflect it.
Agathos 7y ago
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...
- karlicoss 7y ago
  I'm a fan of cool type systems and Haskell in particular too. Also doing lots of messing with data for personal stuff (e.g. https://beepb00p.xyz/mypkg.html#examples https://beepb00p.xyz/mypkg.html#examples). But yep, at least for me, the reality is if I need some quick yet useful code, Python happens to get me there very fast, just because of the sheer amount of code people already have written in Python.
mplanchard 7y ago
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/ https://pypi.org/project/safetywrap/
- dbrgn 7y ago
  At first glance, this looks really solid! Maybe I can deprecate my result library now :D

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 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.html#type-guards-and-differentiating-types 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.

uryga 7y ago
> Does mypy have type guards? not yet, maybe in the future. might be possible to emulate some use cases with Literal Types. tracking issue: https://github.com/python/mypy/issues/5206 https://github.com/python/mypy/issues/5206
karlicoss 7y ago
Oh, not sure how I missed these methods, thanks! I'll update the post to reflect it.

Agathos 7y ago

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...

karlicoss 7y ago
I'm a fan of cool type systems and Haskell in particular too. Also doing lots of messing with data for personal stuff (e.g. https://beepb00p.xyz/mypkg.html#examples https://beepb00p.xyz/mypkg.html#examples). But yep, at least for me, the reality is if I need some quick yet useful code, Python happens to get me there very fast, just because of the sheer amount of code people already have written in Python.

mplanchard 7y ago

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/ https://pypi.org/project/safetywrap/

dbrgn 7y ago
At first glance, this looks really solid! Maybe I can deprecate my result library now :D