fellow openSUSErs, with the advent of Python 3 and still almost unnoticeable decline of Python 2, i have come to a realization that the way we separate them into "python" and "python3" is less than ideal. The granularity of this can be often too coarse (you can't run two apps requiring two different python2 versions, unless they are specifically packaged and bring their own python runtime package), and too fine at the same time (there are already packages that don't actually care whether they run in python 2 or 3) In the spirit of fixing what ain't broken, I humbly propose a grand plan: let's turn "python" into "python2.7", "python3" into "python3.3", and tinker with Provides until it all works just fine. Then, as a last step, symlink /usr/bin/python into /etc/alternatives and let the users pick whichever runtime they like better. This would probably go better if broken into several phases. My current idea is this: Phase 1: - rename "python" to "python2.7", providing "python = 2.7" - rename "python3" to "python3.3", providing "python3 = 3.3" - install the update-alternatives symlink Impact: - Unsure of what would happen on package upgrade. Would we need Obsoletes/Provides combo for this? Perhaps we'd have to create the metapackages outlined in the following phases at this point already. Phase 2: - unify RPM macros - python3 will have %py_(something) macros as well as %py3_(something) macros, the %py3_ versions being aliases to the %py_ versions - make python2.7 provide "python2 = 2.7" instead of "python = 2.7" - make a "python" meta-package requiring, at this time, python2 - each pythonX.Y package now only installs /usr/bin/pythonX.Y binary, python2 and python3 are alternatives for python2.Y and python3.Y respectively, and python is an alternative for either python2, python3, or a specific version. I don't know update-alternatives too well - is this even viable? Impact: - this should mark a clear upgrade path for each of the python variants and for the systemwide "default python" as well - at this phase, i would like to make it possible to build a package for any python (2 or 3 or 50) from the same specfile. i'm not sure that these outlined steps are enough, though. Originally I thought that every python would provide "python = X.Y" and the packages could select which "Requires: python" to pick through package or project meta. But that would result in a horrible breakage, and we need "python" as a separate package for upgrading in any case. We could use "python(abi)" symbol for this, or do the same just with "python-devel"? Any other options? Phase 3A: - when python 3.4 comes out, introduce a new package "python3.4", new meta-package "python3" requiring "python3.4", and corresponding alternatives Impact: - This is the other difficult one. What about lifetime of the pythonX.Y packages? What happens with old systems on perpetual-upgrade? Such as tumbleweed - will the old python runtimes rot there forever-and-ever, or can we force uninstall at some point? Perhaps "Obsoletes: python3 < 3.x" in the "python3" metapackage? Which versions do we support? The newest and the most popular, probably? I know we do something similar with gcc, how does it work there? Phase 3B: - steal and improve Debian's python-central (or however they call it these days) - designate /usr/lib/python-central or something similar for packages that don't want to depend on a specific python runtime version - introduce %post/%postun scriptlet macros for packages that would compile bytecode in /usr/lib/python-central for all known python runtimes on the system, and for pythons so that they compile every package for their versions. This is now actually fully supported by upstream, we can have as many different versions of bytecode for the -same- .py file as we want. Impact: - package can specify "Requires: python" and Just Work(tm) from now until eternity, or until it runs into a deprecated API. Or specify a range of pythons it wants to support - by the time we get here, I'm sure RPM will allow that ;e) With a limited ABI in python3, this can even work for arch-based packages across python minor versions. Phase 4: - when we decide to switch to python3 system-wide, make "python" require "python3" instead of "python2", change default alternative, and be done with it Impact: - breakage of packages still incompatible at that time. that will help us see what needs fixing and what needs to explicitly specify that it wants python2. Somewhere in this is lurking a possibility of supporting different python runtimes such as Jython, Cython, PyPy and whatever else crops up. That's neat, too. Thanks for your attention. Comments, questions? regards m. -- To unsubscribe, e-mail: opensuse-factory+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-factory+owner@opensuse.org