Signed-off-by: Michał Górny <mgo...@gentoo.org> --- .../2021-04-29-python3-9.en.txt | 93 +++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 2021-04-29-python3-9/2021-04-29-python3-9.en.txt
diff --git a/2021-04-29-python3-9/2021-04-29-python3-9.en.txt b/2021-04-29-python3-9/2021-04-29-python3-9.en.txt new file mode 100644 index 0000000..3075d72 --- /dev/null +++ b/2021-04-29-python3-9/2021-04-29-python3-9.en.txt @@ -0,0 +1,93 @@ +Title: Python 3.9 to become the default on 2021-06-01 +Author: Michał Górny <mgo...@gentoo.org> +Posted: 2021-04-29 +Revision: 1 +News-Item-Format: 2.0 +Display-If-Installed: dev-lang/python:3.7 +Display-If-Installed: dev-lang/python:3.8 + +We are planning to switch the default Python target of Gentoo systems +on 2021-06-01, from Python 3.8 to Python 3.9. If you have not changed +the values of PYTHON_TARGETS or PYTHON_SINGLE_TARGET, the change will +have immediate effect on your system and the package manager will try +to switch automatically on the next upgrade following the change. +If you did change the values, prefer a safer approach or have problems +with the update, read on. + +Please note that the default upgrade method switches packages to the new +Python versions as they are rebuilt. This means that all interdependent +packages have to support the new version for the upgrade to proceed, +and that some programs may temporarily fail to find their dependencies +throughout the upgrade (although programs that are already started +are unlikely to be affected). + + +If you wish to avoid changing Python targets at this moment, you can +force the old targets by setting your /etc/portage/package.use to e.g.: + + */* PYTHON_TARGETS: -* python3_8 + */* PYTHON_SINGLE_TARGET: -* python3_8 + +This will enforce Python 3.8 as the current target choice and block +any future updates. However, please note that this solution will only +be suitable for a few more months and you will eventually need to +perform the migration. + + +If you wish to use a safer approach to the migration and temporarily +preserve the support for Python 3.8 and Python 3.9 simultaneously, +set /etc/portage/package.use to: + + */* PYTHON_TARGETS: -* python3_8 python3_9 + */* PYTHON_SINGLE_TARGET: -* python3_8 + +Afterwards, rebuild your system with emerge's --changed-use option or +equivalent. This will cause your packages to gain Python 3.9 support +while preserving Python 3.8 support whenever possible. Then, change +the second line to: + + */* PYTHON_SINGLE_TARGET: -* python3_9 + +This will switch packages that can not support two Python versions +simultaneously, to use Python 3.9. Rebuild again. Finally, switch +the first line to the final version: + + */* PYTHON_TARGETS: -* python3_9 + +The next --changed-use rebuild will remove Python 3.8 support from your +packages. + + +You can also switch to Python 3.9 earlier by setting: + + */* PYTHON_TARGETS: -* python3_9 + */* PYTHON_SINGLE_TARGET: -* python3_9 + +If you choose to follow this or the previous approach, you may want to +remove the package.use overrides after the switch or just leave them +in place to protect your system from the next automatic upgrade +of Python. + + +The Python 3.8 cleanup requires that Python 3.8 is removed from complete +dependency trees in batch. If some of the installed packages using +an older Python version are not triaged for the upgrade, the package +manager will throw dependency conflicts. This makes it important that +the upgrade is carried via a --deep --changed-use @world upgrade, +as well as that any stray packages are removed prior to it, e.g.: + + emerge --depclean + emerge -1vUD @world + emerge --depclean + + +By the time of the switch, it is quite probable that Python 3.10 will +already be available in ~arch Gentoo. Users wishing a more bleeding +edge experience may wish to switch to python3_10 target instead. +However, this is currently discouraged on stable as it will require +unmasking multiple ~arch packages as they gain Python 3.10 support. + +If you have PYTHON_TARGETS or PYTHON_SINGLE_TARGET declared +in make.conf, it is strongly recommended to remove the declarations +and use package.use as presented above. Use of make.conf to set flags +is discouraged as it does not respect package defaults. -- 2.31.1
