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Signed-off-by: Michał Górny <mgorny@g.o> |
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--- |
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.../2021-04-29-python3-9.en.txt | 119 ++++++++++++++++++ |
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1 file changed, 119 insertions(+) |
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create mode 100644 2021-04-29-python3-9/2021-04-29-python3-9.en.txt |
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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 |
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new file mode 100644 |
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index 0000000..fc55427 |
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--- /dev/null |
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+++ b/2021-04-29-python3-9/2021-04-29-python3-9.en.txt |
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@@ -0,0 +1,119 @@ |
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+Title: Python 3.9 to become the default on 2021-06-01 |
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+Author: Michał Górny <mgorny@g.o> |
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+Posted: 2021-04-29 |
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+Revision: 1 |
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+News-Item-Format: 2.0 |
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+Display-If-Installed: dev-lang/python:3.7 |
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+Display-If-Installed: dev-lang/python:3.8 |
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+ |
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+We are planning to switch the default Python target of Gentoo systems |
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+on 2021-06-01, from Python 3.8 to Python 3.9. 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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+ |
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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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+ |
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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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+ |
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+ |
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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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+ |
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+ |
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+At this point, you have a few configuration options to choose from: |
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+ |
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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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+ |
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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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+ |
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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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+ |
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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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+ |
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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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+ |
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+ |
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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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+ |
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+ */* PYTHON_TARGETS: -* python3_8 |
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+ */* PYTHON_SINGLE_TARGET: -* python3_8 |
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+ |
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+This will enforce Python 3.8 and block any future updates. However, |
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+please note that this solution will only be suitable for a few more |
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+months and you will eventually need to perform the migration. |
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+ |
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+ |
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+Forcing the upgrade |
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+=================== |
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+To force the upgrade earlier, explicitly set Python 3.9 targets: |
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+ |
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+ */* PYTHON_TARGETS: -* python3_9 |
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+ */* PYTHON_SINGLE_TARGET: -* python3_9 |
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+ |
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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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+ |
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+ |
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+Safer upgrade procedure |
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+======================= |
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+A safer approach is to add Python 3.9 support to your system first, |
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+and only then remove Python 3.8. However, note that 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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+ |
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+First, enable both Python 3.8 and Python 3.9, and then run the upgrade |
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+commands: |
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+ |
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+ */* PYTHON_TARGETS: -* python3_8 python3_9 |
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+ */* PYTHON_SINGLE_TARGET: -* python3_8 |
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+ |
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+Then switch PYTHON_SINGLE_TARGET and run a second batch of upgrades: |
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+ |
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+ */* PYTHON_TARGETS: -* python3_8 python3_9 |
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+ */* PYTHON_SINGLE_TARGET: -* python3_9 |
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+ |
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+Finally, switch to the final version and upgrade: |
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+ |
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+ */* PYTHON_TARGETS: -* python3_9 |
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+ */* PYTHON_SINGLE_TARGET: -* python3_9 |
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+ |
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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 3.10, and upgrade manually then. |
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+ |
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+ |
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+Upgrade commands |
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+================ |
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+The Python 3.8 cleanup requires that Python 3.8 is removed from complete |
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+dependency trees in batch. If some of the installed packages using |
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+an older Python version are not triaged for the upgrade, the package |
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+manager will throw dependency conflicts. This makes it important that |
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+the upgrade is carried via a --deep --changed-use @world upgrade, |
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+as well as that any stray packages are removed prior to it, e.g.: |
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+ |
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+ emerge --depclean |
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+ emerge -1vUD @world |
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+ emerge --depclean |
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-- |
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2.31.1 |