On Sun, Nov 17, 2019 at 8:09 PM Brad Hubbard <bhubbard(a)redhat.com> wrote: Apologies if this has already been mentioned, but FYI, Fedora (and RHEL and CentOS by extension) do not allow ambiguous python shebangs – they _require_ explicit versioned shebangs. I presume that is what is meant by a hard change to Python3. things like: #!/usr/bin/env python #!/usr/bin/python are not permitted. (Also not #!/usr/bin/env $anything) Shebangs – if there is one – in .py files must be either #!/usr/bin/python3 or #!/usr/bin/python2 AFAIK Fedora is enforcing it, kinda. Package builds in fedora run rpmlint which checks for these kinds of things, although I'm not sure this is a test yet or if there is a test that it scores high enough to fail a build. (Ditto for package builds in the OpenSUSE OBS, i.e. they also run rpmlint, although I haven't noticed python shebang tests there either.)

> > > > > I was very surprised to find out that, in SLES and openSUSE, the symlink > > /usr/bin/python -> /usr/bin/python2 will not be changed even when the > > migration of the underlying distro to Python 3 is complete. > > > > But then my colleagues explained why that is, and I "saw the light". > > Since every single script in the distro has to be audited for Python 3 > > compatibility, anyway, it makes sense to have the shebang be an explicit > > declaration of said compatibility. > > > > By retaining the symlink at it is, all scripts start out the migration > > process with an explicit declaration that they are compatible with > > Python 2. Compatibility with Python 3 is signalled not by saying "it's > > OK with Python 3, we tried it". It's signalled by changing the shebang. > > > > And this isn't unique to SUSE. Fedora is treating the shebang in the > > same way, apparently. [2] > > Seems that if you only have python3 installed in Fedora31 this is > *not* the case. > > # python --version > Python 3.7.5 > # /usr/bin/python --version > Python 3.7.5 > # ls -l /usr/bin/python > lrwxrwxrwx. 1 root root 9 Nov 18 00:57 /usr/bin/python -> ./python3 > > See https://lists.fedoraproject.org/archives/list/devel-announce@lists.fedorapr… > and https://fedoraproject.org/wiki/Changes/RetirePython2#The_python27_package > > "there is no /usr/bin/python" > > So the two distros are quite divergent in their approach apparently? > > > > > It may be true that a given script is fine with Python 3, but as long as > > the shebang says "python" (i.e. python2), there's no way to really find > > out, is there? (Barring things like Josh's suggestion of changing the > > shebang on the fly via a teuthology task/workunit, which is fine if we > > decide we need a transition period, which it looks like we will.) > > > > Nathan > > > > [1] > > https://github.com/kubernetes-incubator/external-storage/blob/master/ceph/c… > > [2] > > https://fedoraproject.org/wiki/FinalizingFedoraSwitchtoPython3#.2Fusr.2Fbin… > > _______________________________________________ > > Sepia mailing list > > Sepia(a)lists.ceph.com > > http://lists.ceph.com/listinfo.cgi/sepia-ceph.com > > > > -- > Cheers, > Brad > _______________________________________________ > Dev mailing list -- dev(a)ceph.io > To unsubscribe send an email to dev-leave(a)ceph.io >

On Sun, Nov 17, 2019 at 8:09 PM Brad Hubbard <bhubbard(a)redhat.com> wrote: Apologies if this has already been mentioned, but FYI, Fedora (and RHEL and CentOS by extension) do not allow ambiguous python shebangs – they _require_ explicit versioned shebangs. I presume that is what is meant by a hard change to Python3. things like: #!/usr/bin/env python #!/usr/bin/python are not permitted. (Also not #!/usr/bin/env $anything) Shebangs – if there is one – in .py files must be either #!/usr/bin/python3 or #!/usr/bin/python2 AFAIK Fedora is enforcing it, kinda. Package builds in fedora run rpmlint which checks for these kinds of things, although I'm not sure this is a test yet or if there is a test that it scores high enough to fail a build. (Ditto for package builds in the OpenSUSE OBS, i.e. they also run rpmlint, although I haven't noticed python shebang tests there either.)

On Mon, Dec 2, 2019 at 2:10 PM Neal Gompa <ngompa13(a)gmail.com> wrote: I forgot to point this out, but the generator only works for Python 3 stuff in EL7, it works for all Python stacks shipped in RHEL for EL8.

-- 真実はいつも一つ！/ Always, there's only one truth!

In Fedora 31, if I have a script with the following shebang: #!/usr/bin/python3 will it not work?

Nathan

Hi Brad: What I'm trying (poorly) to say is: as long as we explicitly state "python3" everywhere and diligently avoid "python", we'll be OK: we will not need to care what "python" points to in a given distro. The motivation for keeping "python -> python2" is/was to avoid breaking legacy scripts. I guess the Fedora folks are not so concerned about that. And it seems reasonable to expect even the more conservative distros to switch over to "python -> python3", at some point in the future - when Python 2 recedes into the cosmic background noise and the fear of breaking older scripts will have subsided. Nathan