[QGIS-Developer] Changes in Python versions on QGIS 3.18

[Sebastian M. Ernst]

Hi Nyall,

> we have absolutely no control
> over the python versions used by many QGIS users. E.g. as a Fedora
> user I've had Python 3.9 for months

is not it safe to say that a clear majority of the user base is running
Windows where you do have full control?

Besides, even in the Linux space, how many "enterprise users" (not
developers) are running "bleeding edge distros" like Fedora or
Tumbleweed? Leap/SLE is stuck at Python 3.6 (and will be for the
foreseeable future [1]), Ubuntu 18.04 LTS is also at 3.6, 20.04 LTS is
at 3.8 (hallelujah), CentOS/RHEL 7 is at 3.6 and even CentOS/RHEL 8
appears to be stuck at 3.6.

As a consequence, going for 3.7 as a minimum requirement effectively
rules out packaging (without intensive patching at least) and (easy) use
on many contemporary LTS Linux distros.

> Given this I think the responsibility lies with the plugin authors to
> ensure they adapt quickly to new Python releases and ensure their
> plugin works correctly in all versions of Python supported by the
> targeted QGIS versions.

Until recently [2], such a constraint did not even exist [3] (other than
a rather broad "Python 3.X"). Now, you're technically sort of supporting
3.7 to 3.9, although it has not been documented anywhere as far as I
know other than in PRs and issues etc. - please correct me if I am wrong.

Sebastian


1:
https://lists.opensuse.org/archives/list/factory@lists.opensuse.org/thread/FLXUTQB6DY4OAZ43AUUKZ6PCOBDAKBRA/#Y6X4QTXPTIPHCBHIO76I5CAT3C75ZEMH
2: https://github.com/qgis/QGIS/pull/41778
3: https://lists.osgeo.org/pipermail/qgis-developer/2020-March/060495.html