DOC/TST: Document numpy 2.0 support and add tests for string array

[lithomas1]

• closes COMPAT/TST: Ensure that numpy 2 string dtype converts to object array in pandas 2.2.x #58104 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[mroeschke]

Curious what happens when dtype=StringDType() is passed to pandas Series or DataFrame constructor? Fine if it doesn't work/converts to object but would be good to note if something unexpected happens

[lithomas1]

I think it silently casts to object.

FWIW, I think the numpy fixed length strings also do this.

[lithomas1]

/preview

[github-actions]

Website preview of this PR available at: https://pandas.pydata.org/preview/pandas-dev/pandas/58202/

[lorentzenchr]

I don't know where to ask: Is there a ETA for pandas 2.2.2 with numpy 2.0(rc) support?

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 2.2.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 5232bee8df3b57766c44b62152aa3fdd24e40ada

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #58202: DOC/TST: Document numpy 2.0 support and add tests for string array'

4. Push to a named branch:

git push YOURFORK 2.2.x:auto-backport-of-pr-58202-on-2.2.x

5. Create a PR against branch 2.2.x, I would have named this PR:

"Backport PR #58202 on branch 2.2.x (DOC/TST: Document numpy 2.0 support and add tests for string array)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

[lithomas1]

I don't know where to ask: Is there a ETA for pandas 2.2.2 with numpy 2.0(rc) support?

Release is expected to happen today.

[lorentzenchr]

@lithomas1 Thanks for the prompt and quite pleasing response 😃