On Mon, Nov 18, 2019 at 12:43 PM Brad Hubbard <bhubbard@xxxxxxxxxx> wrote: > > On Mon, Nov 18, 2019 at 12:17 PM Kaleb Keithley <kkeithle@xxxxxxxxxx> wrote: > > > > On Sun, Nov 17, 2019 at 8:09 PM Brad Hubbard <bhubbard@xxxxxxxxxx> wrote: > >> > >> On Wed, Apr 18, 2018 at 6:27 AM Nathan Cutler <ncutler@xxxxxxx> wrote: > >> > > That would be at odds to what Nathan is suggesting though, which is a > >> > > hard change to Python 3. > >> > >> > > >> > Hm, not sure what hard/soft means in this context. For any given script, > >> > either it runs with Python 3, or it doesn't. And this is determined by > >> > the shebang. (Unless the shebang is omitted, of course.) > > > > > > 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.) > > Does this mean you can no longer write a script that supports both > python 2 and 3? Or, you can write it that way but it will only ever be > run against python2 OR python3 so there is no point? Is it expected > you would need two versions of a script if you wish to support both? I > realise questions of supporting both become less important going > forward and that the emphasis should be on migration to python 3 but > I'm interested in the answers to these questions nonetheless (not > placing the burden of answering them solely on your shoulders Kaleb). Ignore this. I must have been having a mega brain-fade when I wrote it and I still can't understand how I even formulated these questions. Sorry for the noise. > > > > > > >> > >> > > >> > 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@xxxxxxxxxxxxxxxxxxxxxxx/thread/NFMFRKHLPUEDXSADCNXJ2N5YHK2JG3PB/ > >> 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/cephfs/cephfs_provisioner/cephfs_provisioner.py#L27 > >> > [2] > >> > https://fedoraproject.org/wiki/FinalizingFedoraSwitchtoPython3#.2Fusr.2Fbin.2Fpython > >> > _______________________________________________ > >> > Sepia mailing list > >> > Sepia@xxxxxxxxxxxxxx > >> > http://lists.ceph.com/listinfo.cgi/sepia-ceph.com > >> > >> > >> > >> -- > >> Cheers, > >> Brad > >> _______________________________________________ > >> Dev mailing list -- dev@xxxxxxx > >> To unsubscribe send an email to dev-leave@xxxxxxx > >> > > > -- > Cheers, > Brad -- Cheers, Brad _______________________________________________ Dev mailing list -- dev@xxxxxxx To unsubscribe send an email to dev-leave@xxxxxxx
