Stop support for Python 3.9

[Carreau]

New major version are a good time to drop support for older versions. I thihnk 3.9 should not be an issue, I woudl argue for removal of 3.10 as well.

[davidbrochart]

Why should we drop Python 3.9, since it has not reached EOL?

[Carreau]

Please read the description of the PR:

• We are doing a major version, so it's a good time to drop.

Also:

• IPython itself has already dropped 3.10
• https://scientific-python.org/specs/spec-0000/
• It makes CI faster.
• We can start using 3.10 only features/types without conditional code.

Waiting for EOL is not a good reason, EOL means that upsrtream have stopped supporting their package, in general it's better to stop before their EOL so that they can stop their support knowing they don't people in the dust.

Saying you need to wait for EOL, is like saying "no it's fine you can use a deprecated feature, it has not been removed.

[Carreau]

Plus explicitly for 3.9, some test are flaky and annoying only on 3.9

[davidbrochart]

These are still not valid reasons IMO.
Also, AFAIK we don't do that in other Jupyter projects.

[Carreau]

Meh, if you don't want that's fine.

I find it a bit strange as for example main numpy is 3.11+, matplotlib is 3.10+ to lag more than 2 years behind and I have a hard time seing how someone that still python 3.9 can justify that they must have ipykernel 7+. It's not like dropping 3.9 support in 7.0 is still going to prevent 6.x to be installed...

Also, AFAIK we don't do that in other Jupyter projects.

This is factually false as IPython does it. Unless you do not consider IPython as a Jupyter project ?

I think you are also adding maintenance burden to yourself and potentially pushing some contributors away.

I personally only have so much free time I'm willing to invest to fix bugs on older Pythons, and there are also limited time I can justify to clients WRT python versions they don't use anymore. The "oh I can't do that because we still support 3.9", writing conditional code for older Python is becoming tiresome.

Feel free to close.

[davidbrochart]

I'm just saying my opinion, thus not closing.
I'm also not saying IPython is not a Jupyter project, but I don't know any other Jupyter project that does what you suggest.

[Carreau]

I'm also not saying IPython is not a Jupyter project, but I don't know any other Jupyter project that does what you suggest.

Ah sure, well, but at the same time some project still advertise compatibility for Python 3.8 (jupyter_core, for example), and I don't think many project have discussed the issue, I'm guessing many rely on the maintainer tools default:

• Bump min Python to 3.9 jupyterlab/maintainer-tools#253
  or bump when they have to:
• Handle newer jupyter_events wants string version, drop 3.8 jupyter-server/jupyter_server#1481

But notebook for example test on 3.9+

• https://github.com/jupyter/notebook/blob/2c66ed390e4e171c3a2dcedd4388411d030a3909/.github/workflows/build.yml#L41
  but advertise itself as 3.8+

But this is again bumps because they had to (in my understanding), and I'd love for project to actually discuss python supported window instead of just doing it as late as possible when it's necessary because this is super painful.

Without planning and a clear written rule it's sometime really hard to have discussion with clients.

I would feel much better to know that ipykernel 7+ is Python 3.11+ only, than to have to say that yes, 7.0 to 7.6 is 3.9+, and 7.7 onward in 3.10+ and to be aware of that at the last minute.

[davidbrochart]

I feel this is something that has to be discussed at the Jupyter level, because one Jupyter project will affect many others, and this is especially true for ipykernel.
My understanding is that we support Python versions until EOL, but I may be wrong.

[ianthomas23]

Personally I am +1 on this.