Drop support for Python 3.10 ?

[kif]

On the one hand, Python 3.10 is still maintained until end 2026, on the other numpy dropped it.
For FabIO, this means there could be a single wheel usable from python 3.11 to 3.14 and forward compatible.
#595

Do we want this feature right now (more realistically in October 2025) or do we postpone this change for a year

[rayosborn]

NeXpy, which has FabIO as a dependency, still supports Python 3.10. However, we haven't had any issues with current versions, so as long as legacy versions remain available, I'm not sure what the problem would be. Is there a list of upcoming changes that won't be available when legacy versions are no longer supported?

[kif]

For now, FabIO supports 3.9 and 3.10. If you need a build for 3.10, it is not very difficult to obtain it, but dropping 3.9 & 3.10 would allow to simplify the distribution of a single wheel per platform instead of 5 or 6.

The only regression I noticed is related to a new version of Glymur which is used for Jpeg2k support.

[rayosborn]

I have voted in support of dropping Python 3.10. PyPI will just satisfy the dependency with an older version.

[da-woods]

In principle you could build a Python 3.10 wheel and a limited API wheel for everything else, so adopting the Limited API doesn't necessarily mean dropping Python 3.10 - you just don't get all of the advantages of it yet, but you do get a reduction in the number of wheels.

I couldn't advise how to do this in Meson though.

I also don't have an opinion on what you should do - I'm just commenting as a Cython developer doing a quick GitHub search to see how people are getting on with the Limited API.

[kif]

Hi David,
Thanks for your interest. On the meson side, it turns out to be extremely simple as demonstrated in https://github.com/silx-kit/fabio/pull/621/files
Just write in the meson.build that limited_api: '3.11' for each extensions and it just compiles.

The limitation between the limited API for python 3.10 and 3.11 comes from those C-function call in several cython extensions:

           ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━┓                                                                                 
           ┃ Symbol                    ┃ Version ┃                                                                                 
           ┡━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━┩                                                                                 
           │ PyType_GetQualName        │ 3.11    │                                                                                 
           │ PyObject_GetBuffer        │ 3.11    │                                                                                 
           │ Py_Version                │ 3.11    │                                                                                 
           │ PyErr_SetHandledException │ 3.11    │                                                                                 
           │ PyBuffer_Release          │ 3.11    │                                                                                 
           └───────────────────────────┴─────────┘

It is easily obtained with the abi3audit tool.

So if I limit to 3.11, it works out of the box, but if I limit to 3.10, there are several extensions that do not compile. Any hint on how to fix them or make them work in python 3.10 would be welcome even though I wonder if it makes sense to rewrite 6 extensions in an obfuscated way just to gain a compatibility that would be granted for free in one year of time (when 3.10 reaches its end-of-support).

[da-woods]

You won't easily replace any of the buffer functions. (The others would be handled automatically by Cython if set a lower limited PI version)

However, I don't think I made my point very well: I was suggesting that you could distribute a regular API 3.10 wheel (as you do now) and a limited API 3.11+ wheel.