----- Original Message ----- > On Fri, Jul 19, 2013 at 08:20:02AM +0200, Marcela Mašláňová wrote: > > On 07/19/2013 05:44 AM, Toshio Kuratomi wrote: > > > > > >On Jul 18, 2013 5:42 PM, "Michael Catanzaro" <mike.catanzaro@xxxxxxxxx > > ><mailto:mike.catanzaro@xxxxxxxxx>> wrote: > > > > > > > > On Thu, 2013-07-18 at 09:53 -0700, Toshio Kuratomi wrote: > > > > > /usr/bin/python should refer to python2 -- > > > > > http://www.python.org/dev/peps/pep-0394/ I'd be -1 to changing this > > > > But when python2 is no longer installed by default, surely you want to > > > > get a python prompt when you type 'python'? > > > > > >Yes, and for a long time, I'm going to want to get a python2 prompt. > > >Which means installing the package for python2, not having python3 start > > >on that case. > > > > > > > > > > > Why do you want to use old version as default? That's very > > conservative approach for Fedora ;-) > > This is the wrong mental model of the relationship between python2 and > python3. As a comparison this argument is akin to saying, "C is the old > version of C++. We should be porting all our code to use the C++ compiler > in Fedora" C is much more compatible to C++ than python2 is to python3 so > this would be a less drastic change. > > python2 and python3 are separate languages. There is a lot of similarity > between the two and with recent enough versions of python2 (2.7) and python3 > (python3.4) and some external libraries (python-six) and by sticking to some > specific coding styles ( http://python3porting.com/noconv.html ) and by > sometimes resorting to having separate files for some python2-specific > routines vs python3-specific routines you can write code that is valid and > runs under either language. That does not mean that they are the same > language. > The problem is that you're basically saying "my mental model is the right one", which is not necessarily true for everyone (and not necessarily true generally). Taking your arguments a bit further, Python 2.6 and 2.7 are different languages too, since there are some backward incompatible additions to Python 2.7. > > Upstream plans to support it until 2015 (maybe little longer). Fedora > > needs to be prepared for such step, so it's the right time to start > > working on it. > > > I am wholeheartedly in favor of "working on it". But things like switching > the default /usr/bin/python are not "working on it". Those are backwards > incompatible, end user visible, changes of expectations that we do not need > to implement now in order to be a leader. When people invoke python, they > expect python2. When they want python3, they expect to type python3 to get > that. At the moment, causing /usr/bin/python to invoke python3 is just > going to cause confusion and end user confusion (arch is the only linux > distro that sets /usr/bin/python to point to python3). > > As an example here, let's suppose that we were to stop shipping firefox by > default and started shipping chromium instead. Would we make > /usr/bin/firefox invoke /usr/bin/chromium? Would we have a firefox icon > that started chromium when clicked? When applied here, it does seem to make > more sense for end user's to notice that there isn't a firefox icon and > either consciously open up a different web browser or else install firefox > to get their preferred browsing experience, right? /usr/bin/python is the > same way. People have tons of scripts on their systems with > #!/usr/bin/python shebang lines. If we change /usr/bin/python to > point to /usr/bin/python3 then we'll force them to deal with either porting, > going through all their scripts and replacing them with /usr/bin/python2, or > switching to another distribution which doesn't change the meanings of well > known interpreter paths for no gain. > Again, this is all based on your "mental model" and on your assumption that it is the correct one. I just don't agree. > All this is not to say that there might not be a time in the future when it > makes sense to have python3 assume the /usr/bin/python name. However, that > time is *after* the collective user consciousness has stopped using > /usr/bin/python, not before. When we can go to pycon and talks are assumed > to be targeting python3 rather than python2. After people wanting to do > a simple calculation on the CLI stop doing /usr/bin/python -c 'print 5 + 6'. > This is probably after alternate python implementations like pypy and jython > either die off or finally make the switch to implementing python3. My guess > is this will be after there's a RHEL release that includes /usr/bin/python3 > in the default install since RHEL and CentOS are major parts of our > ecosystem and will have to be able to use the python3 syntax on both their > RHEL servers and Fedora machines. To some extent, this also depends on what > other large distros set as their expectations: Debian and Ubuntu currently > point /usr/bin/python to python2. AFAIK, only Arch is pointing to python3. > My intuition is this will be at least two years after we stop shipping > /usr/bin/python (pointing to python2) by default but this could be wrong -- > it's about the expectations of the Fedora community and the Linux and python > development communities as a whole. > > -Toshio -- Regards, Bohuslav "Slavek" Kabrda. -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
