Add Type and Final pandas._typing

[vaibhavhrt]

Since we are not merging #25975 Type and Final needs to be added to pandas._typing module.

Final is required for PR #25961
Type is required to stay compatible with python 3.5.1 as Type was added in 3.5.2 python docs

[vaibhavhrt]

PR on the way...

[vaibhavhrt]

On second thought it looks too complicated and time consuming for me. Someone else please pick it up. @TomAugspurger maybe you would be interested in it.

[jreback]

you can pretty much just directly vendor typing_extensions

[vaibhavhrt]

@jreback I think you mean copy paste the relevant parts from the source code of typing_extensions. I took a look at their source code but it's a bit complicated for me. I will take a look at it again after a few days when I get some time and see what I can do.

[TomAugspurger]

What benefit do we get from adding Final to these annotations?

[WillAyd]

Final would just indicate that a variable is not supposed to be subsequently modified.

FWIW I consider it to be a nice to have but not a blocker in the PR where it is mentioned. If we consider bumping min Python version to 3.5.2 then alternately we don’t need to vendor anything

[gfyoung]

My preference is to vendor for now. Bumping min Python version, not matter how small, is still a relatively big change to codebase.

[TomAugspurger]

My preference is to just not add these annotations.

…

On Apr 23, 2019, at 01:16, gfyoung ***@***.***> wrote: My preference is to vendor for now. Bumping min Python version, not matter how small, is still a relative big change to codebase. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[WillAyd]

My preference is to just not add these annotations.

Final is fine to ignore. I think Type[] is very useful though and that didn't appear until 3.5.2 along with a few (less critical IMO) items:

https://docs.python.org/3.5/whatsnew/changelog.html#id28

My preference is to vendor for now. Bumping min Python version, not matter how small, is still a relative big change to codebase.

Have we bumped bug fix releases in the past? We are already dropping Py27 this release so wondering if moving to 3.5.2 from there is adding incremental risk

[gfyoung]

I don't recall if we have done incremental bumps like this in the past, but if there is interest, I think that should discussion should be handled separately in another issue / PR.

[WillAyd]

Closing this as is. Can discuss move to 3.5.2 in another issue