Re: [gentoo-dev] [News item review v4] Python preference to follow PYTHON_TARGETS
Hi, Changed eselect-python dep removal date to July 2021. Not sure if there's a reason to display it to stable users today, or delay until the stable request is actually filed. ``` Title: Python preference to follow PYTHON_TARGETS Author: Michał Górny Posted: 2021-01-24 Revision: 1 News-Item-Format: 2.0 On 2021-02-01 stable users will switch to a new method of updating the preferred Python versions that employs the configuration update mechanism in order to follow PYTHON_TARGETS. We will also deprecate app-eselect/eselect-python, and it will stop being installed by default after 2021-07-01. If you wish to use the newest Python version present in your PYTHON_TARGETS, you only have to accept configuration changes. If you wish to customize the behavior, read on. Since 2017, /usr/bin/python and the related non-versioned symlinks are wrapped through dev-lang/python-exec. The list of preferred Python implementations is stored in /etc/python-exec/python-exec.conf and/or per-program /etc/python-exec/.conf configuration files. To preserve backwards compatibility, app-eselect/eselect-python remained a wrapper that updated this file. However, this mechanism alone has proven inconvenient to end users who had to update python-exec.conf whenever the default PYTHON_TARGETS changed. Thanks to the fallback logic, this was not a major problem for software installed via Gentoo packages that always ensure that a supported implementation is used. However, users have reported that whenever the preference for /usr/bin/python mismatched their PYTHON_TARGETS, their custom scripts would break due to unsatisfied dependencies. This does not follow the principle of least surprise. For this reason, we have decided to change the default python-exec configuration to match PYTHON_TARGETS by default, in the eclass preference order, that is from the newest CPython version to oldest, with alternative Python implementations coming afterwards. This change will be propagated via the configuration protection mechanism whenever dev-lang/python-exec-conf is installed or rebuilt due to PYTHON_TARGETS changes. This will permit the users to interactively confirm the updates. If the new default is not correct for you, please use your preferred configuration update tool to discard or edit the new configuration file. Furthermore, dev-lang/python will no longer attempt to automatically update the Python interpreter preference, or pull in eselect-python automatically. If you wish to continue using it, please install/record it explicitly to ensure that it is not unmerged, e.g.: emerge -n app-eselect/eselect-python ``` -- Best regards, Michał Górny
Re: [gentoo-dev] [News item review v4] Python preference to follow PYTHON_TARGETS
210125 Michał Górny wrote: > Changed eselect-python dep removal date to July 2021. > Not sure if there's a reason to display it to stable users today, > or delay until the stable request is actually filed. I've been using Gentoo since 2003 , happily enough most of the time ; I'm an ordinary desktop user without any special requirements. Python versions have been one of the reasons for the exceptions. I finally managed to remove 2.7 from my system yesterday. I do appreciate your work in this area, but I can make no sense of the news item below. > Title: Python preference to follow PYTHON_TARGETS > Author: Michał Górny > Posted: 2021-01-24 > Revision: 1 > News-Item-Format: 2.0 > > On 2021-02-01 stable users will switch to a new method of updating > the preferred Python versions that employs the configuration update > mechanism in order to follow PYTHON_TARGETS. What are "preferred Python versions" ? Why are they multiple, not one ? What is the "configuration update mechanism", how does it "follow PYTHON_TARGETS" & why are they both needed ? > We will also deprecate app-eselect/eselect-python, > and it will stop being installed by default after 2021-07-01. Why has there been this 3rd method of managing Python versions ? Why might it still be needed by users ? > If you wish to use the newest Python version present > in your PYTHON_TARGETS, you only have to accept configuration changes. Why doesn't Python behave like most other packages, ie use the latest installed version ? Why does PYTHON_TARGETS exist ? Why are the "targets" ? -- it sounds as if they may not be achieved. What are the "configuration changes" ? Do you mean those in /etc/python-exec ? > If you wish to customize the behavior, read on. I have no wish to customise Python. I don't use it to develop programs ; it is installed only as a requirement for other packages, eg Portage. I do use it for a small script to work as a CLI calculator. Given this, I won't comment on the rest of the news item, but it makes even less sense to me than the section above. In /etc/portage/make.conf , I have USE_PYTHON="2.7 3.5 3.6" PYTHON_TARGETS="python3_7" PYTHON_SINGLE_TARGET="python3_7" 'eselect python list' gives Available Python interpreters, in order of preference: [1] python3.7 [2] python3.6 (uninstalled) /etc/python-exec/ contains 1 file 'python-exec.conf', which says (besides many lines of comment) : python3.7 python3.6 'eix python' shows [I] dev-lang/python Available versions: (2.7) 2.7.18-r5 ~2.7.18-r6 (3.6) 3.6.12-r1(3.6/3.6m)^t ~3.6.12-r2(3.6/3.6m)^t (3.7) 3.7.9-r1(3.7/3.7m)^t ~3.7.9-r2(3.7/3.7m)^t (3.8) 3.8.6-r1^t ~3.8.7-r1^t (3.9) 3.9.0-r1^t ~3.9.1-r1^t (3.10) ~3.10.0_alpha3-r1^t ~3.10.0_alpha4^t {-berkdb bluetooth build examples gdbm hardened ipv6 libressl +ncurses +readline sqlite +ssl test +threads tk verify-sig +wide-unicode wininst +xml ELIBC="uclibc"} Installed versions: 3.7.9-r1(3.7/3.7m)^t([2021-01-24 23:26:15])(gdbm ncurses readline sqlite ssl tk xml -bluetooth -build -examples -hardened -ipv6 -libressl -test -wininst) 3.8.6-r1(3.8)^t([2021-01-24 23:28:48])(gdbm ncurses readline sqlite ssl tk xml -bluetooth -build -examples -hardened -ipv6 -libressl -test -wininst) 3.9.0-r1(3.9)^t([2021-01-24 23:31:53])(gdbm ncurses readline sqlite ssl tk xml -bluetooth -build -examples -hardened -ipv6 -libressl -test -wininst) I can't understand why there are so many ways to control Python nor which one users are supposed to use nor how to reconcile them. I would be very happy simply to use 3.9 for all Python purposes. Thanks again for your hard work on this + other areas of Gentoo. -- ,, SUPPORT ___//___, Philip Webb ELECTRIC /] [] [] [] [] []| Cities Centre, University of Toronto TRANSIT`-O--O---' purslowatcadotinterdotnet
Re: [gentoo-dev] [News item review v4] Python preference to follow PYTHON_TARGETS
On Tue, 2021-01-26 at 01:39 -0500, Philip Webb wrote: > 210125 Michał Górny wrote: > > Changed eselect-python dep removal date to July 2021. > > Not sure if there's a reason to display it to stable users today, > > or delay until the stable request is actually filed. > > I've been using Gentoo since 2003 , happily enough most of the time ; > I'm an ordinary desktop user without any special requirements. > Python versions have been one of the reasons for the exceptions. > I finally managed to remove 2.7 from my system yesterday. > > I do appreciate your work in this area, > but I can make no sense of the news item below. Thank you for your kind words. However, I don't really know if I can help you. The news item is supposed to tell what's new. If I were to keep explaining the basics, it'd become too long (and people are already complaining that my items are getting too long). I think this falls into 'if you don't know whether you need to read on, don't'. > > > Title: Python preference to follow PYTHON_TARGETS > > Author: Michał Górny > > Posted: 2021-01-24 > > Revision: 1 > > News-Item-Format: 2.0 > > > > On 2021-02-01 stable users will switch to a new method of updating > > the preferred Python versions that employs the configuration update > > mechanism in order to follow PYTHON_TARGETS. > > What are "preferred Python versions" ? Why are they multiple, not one ? It's the order in which the Python version used to run stuff are used. There are multiple because not all impls are actually supported by everything -- so if your top preference doesn't work, it goes for the second top, etc. > What is the "configuration update mechanism", CONFIG_PROTECT / etc-update / dispatch-conf. > how does it "follow PYTHON_TARGETS" & why are they both needed ? I think this is explained below -- it generates python-exec.conf based on PYTHON_TARGETS. Both are needed because we can't technically combine both without putting a lot of effort to implement stuff that's going to be slow and unreliable. > > > We will also deprecate app-eselect/eselect-python, > > and it will stop being installed by default after 2021-07-01. > > Why has there been this 3rd method of managing Python versions ? > Why might it still be needed by users ? Historical reasons, as always. Backwards compatibility. > > If you wish to use the newest Python version present > > in your PYTHON_TARGETS, you only have to accept configuration changes. > > Why doesn't Python behave like most other packages, > ie use the latest installed version ? Why does PYTHON_TARGETS exist ? > Why are the "targets" ? -- it sounds as if they may not be achieved. Because Python versions are not ABI-compatible, and old packages are usually broken with new major Python releases. It takes a lot of testing, patching, bumping to support it. > What are the "configuration changes" ? > Do you mean those in /etc/python-exec ? Yes. > > > If you wish to customize the behavior, read on. > > I have no wish to customise Python. I don't use it to develop programs ; > it is installed only as a requirement for other packages, eg Portage. > I do use it for a small script to work as a CLI calculator. > Given this, I won't comment on the rest of the news item, > but it makes even less sense to me than the section above. Then you don't have to do anything. -- Best regards, Michał Górny