Python 3.12 migration and Python 3.11 by default

#2011

Co-authored-by: Uwe L. Korn <[email protected]>

Author: jaimergp

news/2023-09-25-python-312-migration-and-python-311-by-default.md

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+# Python 3.12 migration and Python 3.11 by default
+
+With the Python 3.12 release approaching, we have already started the
+rebuild of packages for it. Although, there is no offical Python 3.12
+release yet, the release candidates of it will have the same ABI. Thus
+packages built with the release candidate can be safely used with the
+later offical release. To support rebuilding packages on conda-forge
+while ensuring Python release candidates don't end up in end-user
+solves, we have uploaded the Python 3.12.0rc2 and rc3 builds to the
+`conda-forge/label/python_rc` channel. The `python312` migration adds
+this channel in the feedstock builds to the Python 3.12 matrix entry. On
+the offical release of Python 3.12, we will adjust the migration and
+remove the channel again. Then (on a rerender), feedstock will only
+consume the main channel again.
+
+Overall, this approach allows us to provide Python 3.12 for a wide range
+of packages already on the day of the offical Python 3.12 release.
+At the same time, we have stopped the Python 3.11 migration and added it
+to the list of default Python versions on conda-forge.