Developers: Continue Supporting Python 3.7?

[adam-grant-hendry]

(@pyvista/developers) @tkoyama010 @akaszynski @adeak

Do we want to continue supporting Python 3.7 for pyvistaqt? There are several packages that won't get updated with 3.7, namely:

• ipython: 7.34.0 -> 8.4.0
• numpy: 1.21.6 -> 1.23.0
• pylint: 2.13.0 -> 2.14.3

It looks like support will end in June of next year, so we have time: PEP 537. However, it would be nice to bump up.

[adeak]

What specific features are you aiming for with 3.8?

[adam-grant-hendry]

• IPython.kernel was deprecated in IPython 8.0. This was a wrapper for ipykernel, so when Python 3.7 sunsets in a year, pyvistaqt will need updating to accomodate the new major changes. (furthermore, ipykernel is type hinted, whereas IPython is not)

• I've helped fix a type hinting bug for Qt slots/signals in pylint via astroid, which would be helpful to have (see PR #1654; probably will make its way in in 2.14.4 though)

Namely, these will help me update type hinting. I can try and get around it for now if we really want to still keep 3.7, but I'll have to fix certain things because dependabot can't bump things up:

• Bump pylint from 2.13.0 to 2.14.3 #175
• Bump numpy from 1.21.6 to 1.23.0 #176
• Bump ipython from 7.34.0 to 8.4.0 #180

I want to see if I should go through the effort if 3.7 is only going to be around 1 more year.

[adeak]

Doesn't the first one mean that we have to look for a replacement anyway? In other words, can we replace IPython.kernel irrespective of a Python version requirement bump?

[adam-grant-hendry]

Only the kernel module in IPython was deprecated. The first one can be handled very simply by using the ipykernel package everywhere IPython.kernel pops up in the source and adding it to requirements_test.txt. Python 3.7 supports the latest version of ipykernel. For that, I'm not terribly concerned. (We should start supporting that transition now though)

For the other, everywhere signals and slots occur and the backend used is PySide6, pylint is going to spit out an error, which might keep me from pushing up changes now that we implemented precommit for pyvistaqt

[adam-grant-hendry]

As an aside, in ci/azure-pipelines.yml, I see we only test against PyQt5==5.11.3. (I know from the docs that we've historically used PyQt5 and are transitioning to qtpy; the PyQt licenses have historically been restrictive, which has prevented us in the past from adding them to the requirements_test.txt.)

In transitioning to qtpy, there are a few subtle testing ramifications:

• There are several differences between PyQt5 < 5.11 and > 5.11 that cause mypy to fail in > 5.11, and PySide6 has fixed several type hinting errors and bugs that plagued pytestqt (see my answer to pytest-qt Function mouseMove() Not Working ).

• For the unsuspecting tester, there is a subtle bug if you install all Qt binding versions and attempt to test (see BUG: Multiple PyQt/PySide Versions Not Supported #437 ). Tests simply won't run and pytest fails silenty.

[tkoyama010]

Thank you for bringing this to our attention. My personal opinion is that PyVista and PyVistaQt should keep pace with the Python end of life. This means that Python 3.7 support should continue until 27 Jun 2023. If there is a problem with package dependencies, I think we should stop updating.

[adam-grant-hendry]

@tkoyama010 Okay, thanks for confirming! No concerns here. May I submit a PR to change to using ipykernel and workarounds for pylint that will still work for Python 3.7?

[tkoyama010]

Pull Request is always welcome.