Formally mark deprecated items in threading for removal in 3.21

[jepler]

Feature or enhancement

Proposal:

Several camelCase names in the threading module have been marked with DeprecationWarnings since 3.10. (they are replaced by snake_case names and in some cases with properties rather than getter/setter functions) However, they have never had a removal version set.

I propose to mark these for removal in 3.21 and will prepare a PR to do so.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-154205: threading: Deprecated items to be removed in 3.21. #154206

[hugovk]

This was originally deprecated in #87889 / #25174 in 3.10.

That PR was going to schedule removal in 3.12, but it was left open-ended due to too many projects still using the old names:

#87889 (comment)

Please can you check how many of the popular PyPI packages still use them? See https://hugovk.dev/blog/2022/how-to-search-5000-python-projects/. A GitHub search can also help gauge use.

Removal in 3.21 in 2032 is probably okay, and a deadline in the warning can prompt action; but would be good to have an idea of how widespread use is now and we can review again before actual removal. If there are projects still using the 2.5 name, PRs to upgrade would be helpful.

[jepler]

I downloaded the top 15000 files and searched with the following pattern:
'\b(\.notifyAll\(|\.isSet\(|activeCount\(\)|\.setDaemon\(|\.isDaemon\(\)|\.setName\(|\.getName\(\))\b'.

Result: Found 653 matching lines in 151 projects.

I think there are many false positives particularly for setName (371 hits across 45 packages) -- however there are a substantial number of hits for setDaemon which I think is less likely to be a false positive (194 across 100 packages).

setDaemon is a small number compared to hits for \.daemon =, 2656 matching lines in 789 projects. So deprecated uses are 7% of all uses but approximately 11% of packages using one or the other are still using the deprecated version.