| # eselect news read 25
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| 2024-05-09-python3-12
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| Title Python 3.12 to become the default on 2024-06-01
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| Author Michał Górny <mgorny@gentoo.org>
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| Posted 2024-05-09
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| Revision 1
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| We are planning to switch the default Python target of Gentoo systems
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| on 2024-06-01, from Python 3.11 to Python 3.12. If you have not changed
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| the values of PYTHON_TARGETS or PYTHON_SINGLE_TARGET, the change will
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| have immediate effect on your system and the package manager will try
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| to switch automatically on the next upgrade following the change.
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| If you did change the values, prefer a safer approach or have problems
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| with the update, read on.
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| Please note that the default upgrade method switches packages to the new
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| Python versions as they are rebuilt. This means that all interdependent
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| packages have to support the new version for the upgrade to proceed,
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| and that some programs may temporarily fail to find their dependencies
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| throughout the upgrade (although programs that are already started
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| are unlikely to be affected).
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| If you have PYTHON_TARGETS or PYTHON_SINGLE_TARGET declared
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| in make.conf, please remove these declarations as they will interfere
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| with the package.use samples provided below. Using make.conf for Python
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| targets is discouraged as it prevents package defaults from applying
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| when necessary. This news item assumes using /etc/portage/package.use
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| or your package manager's equivalent file for configuration.
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| At this point, you have a few configuration options to choose from:
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| 1. If you wish Python upgrades to apply automatically, you can remove
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| PYTHON_TARGETS and PYTHON_SINGLE_TARGET declarations. When
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| the defaults change, your package manager should handle the upgrade
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| automatically. However, you may still need to run the update
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| commands if any problems arise.
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| 2. If you wish to defer the upgrade for the time being, you can
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| explicitly set the old values in package.use.
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| 3. If you wish to force the upgrade earlier, you can explicitly set
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| the new values and run the upgrade commands.
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| 4. If you wish to use a safer approach (i.e. less likely to temporarily
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| break packages during the upgrade), you can perform a multi-step
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| upgrade as outlined below.
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| 5. Finally, you can use an arbitrary combination of PYTHON_TARGETS
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| and PYTHON_SINGLE_TARGET.
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| Deferring the upgrade
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| =====================
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| To defer the upgrade, explicitly set the old targets:
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| */* PYTHON_TARGETS: -* python3_11
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| */* PYTHON_SINGLE_TARGET: -* python3_11
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| This will enforce Python 3.11 and block any future updates. However,
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| please note that this is only a temporary solution and you will
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| eventually need to perform the migration.
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| Forcing the upgrade
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| ===================
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| To force the upgrade earlier, explicitly select the Python 3.12 targets:
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| */* PYTHON_TARGETS: -* python3_12
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| */* PYTHON_SINGLE_TARGET: -* python3_12
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| However, it is important to remember to remove this after the defaults
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| change, as it will interfere with the automatic switch to the next
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| Python version in the future.
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| Safer upgrade procedure
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| =======================
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| A safer approach is to add Python 3.12 support to your system first,
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| and only then remove Python 3.11. However, note that this involves two
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| rebuilds of all the affected packages, so it will take noticeably
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| longer.
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| First, enable both Python 3.11 and Python 3.12, and then run the upgrade
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| commands:
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| */* PYTHON_TARGETS: -* python3_11 python3_12
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| */* PYTHON_SINGLE_TARGET: -* python3_11
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| Then switch PYTHON_SINGLE_TARGET and run the second batch of upgrades:
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| */* PYTHON_TARGETS: -* python3_11 python3_12
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| */* PYTHON_SINGLE_TARGET: -* python3_12
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| Finally, switch to the final version and upgrade:
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| */* PYTHON_TARGETS: -* python3_12
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| */* PYTHON_SINGLE_TARGET: -* python3_12
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| You may wish to remove the target overrides after the defaults switch.
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| Alternatively, you can keep them to block the next automatic upgrade
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| to Python 3.13, and upgrade manually then.
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| Upgrade commands
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| ================
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| The Python 3.11 cleanup requires that Python 3.11 is removed from
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| the complete dependency trees in batch. If some of the
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| installed packages using an older Python version are not triaged
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| for the upgrade, the package manager will throw dependency conflicts.
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| This makes it important that the upgrade is carried via a --deep
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| --changed-use @world upgrade, as well as that any stray packages
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| are removed prior to it, e.g.:
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| emerge --depclean
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| emerge -1vUD @world
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| emerge --depclean
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