Fedora Linux will switch to Python 3 by default

https://fedoraproject.org/wiki/Changes/Python_3_as_Default

by Tsiolkovsky • 13 years ago

188 71 13 years ago

dancecodes3• 13 years ago

it so bravery

jol2• 13 years ago

Ok, so I'll state the obvious - it took almost 6 years from release of python 3.0.0 (2008-12-03)[1] till fedora adopting it. And I thought that cheap PHP hosts takes long time to upgrade PHP version.

Can someone with knowledge of python ecosystem explain what took a major distro so long, given that you could run different versions of python in parallel (or couldn't you?) for some of big pro software that needs the old version? [1] - http://python.org/download/releases/3.0/

dancecodes3• 13 years ago

gentoo?

python 3.2.5 there (and not so later) by default and you can run oldest versions in parallel also

jol2• 13 years ago

ok, but what took so long for fedora? (in other comment I read about ubuntu waiting just almost 5 years) why?

jliechti1• 13 years ago

You can see some reasons from one of the core developers here [0]:

"We (i.e. the Python core developers) predicted when Python 3.0 was released that it would take about 5 years for 3.x to become the "default" choice for new projects over the 2.x series."

He suggests the 5 year timeline begins in June 2009 with the release of 3.1 (since 3.0 still had many bugs) - so that means there is a little more than half a year left for it to become the default, if the prediction holds true.

The rest of his post goes into the issues in adopting Python 3.x.

[0] http://programmers.stackexchange.com/questions/63859/why-do-...

vdaniuk• 13 years ago

Thanks for sharing this information. I am interested what strategies can be applied to increase the speed of language adoption.

qznc3• 13 years ago

Twisted is one of the more important projects without Python3 support. This is their overview: http://twistedmatrix.com/trac/wiki/Plan/Python3

Tobu• 13 years ago

Twisted is 99% ported and already packaged in Ubuntu: http://packages.ubuntu.com/raring/python3-twisted-experiment...

qznc3• 13 years ago

The article provides a link to the TODO list: https://fedoraproject.org/wiki/User:Churchyard/python3

gnur• 13 years ago

One of the main differences with different PHP versions is that python 3 is not backwards compatible. Also, even after all these years, there are still quite some python projects that don't support python 3 (examples: mysqldb/twisted). Just switching the interpreter from 2 to 3 is surely something that will give a lot of headaches.

alcari• 13 years ago

No, PHP minor versions are not necessarily compatible with each other. When I worked in web hosting, we had to deal with quite a few issues resulting from changes between 5.2 and 5.3, and later 5.3 and 5.4.

At least Python has a sane versioning scheme, where breaking compatibility increments the major version number or is a bug.

andrewaylett• 13 years ago

It's not that it's not there -- Python 3 has been available on Fedora for years. It's that the system tools which use Python still use Python 2, which is itself still a modern, supported environment. TBH, I think it's probably correct for critical system scripts to be more conservative in upgrading.

It's also still going to be a while before Python 2 is actually removed, and while both are available the `python` executable will continue to point to Python 2.

If you don't ask for Python at the moment, you'll still get in your base install, because the system uses it. You get Python 2. In the future, you'll get Python 3 instead.

sho_hn2• 13 years ago

I think you may just be confused about the specifics of "adopting it".

Python 3 has been packaged and co-installable in Fedora for many years, and likewise a large number of Python 3 libraries are also packaged, and Fedora even put in quite a bunch of effort into tracking and increasing that number via porting efforts. And thanks to all of that, things are now getting ready to abandon Python 2 for the most core parts of the system itself.

So it's not like those six were spent idle, rather they were in the process of "adopting it" for much of those six years, and this is simply another milestone in that process.

If you were a user of the system and wanted to run something against Python 3, you could do that for a long time now. I've written plenty of Python 3 on Fedora systems using nothing but system packages.

shuzchen2• 13 years ago

The switch isn't making python3 available; both python2 and python3 have been available for users for a long time. The switch means having the system tools rely on python3 rather than on python2, such that you can successfully install, boot, and configure a Fedora install without python2. This involved porting all the system code that uses python.

I suspect Archlinux's job was easy, because they had fewer system tools that utilized python. For example, Pacman (Arch's package manager) is written in C, whereas Yum (Fedora's package manager) is written in Python. Fedora also has other components that use python (the firewall frontend, some build/install/setup scripts), and "switching" to python3 involves porting over all of that.

fulafel2• 13 years ago

Python 3 was adopted in Fedora 13. 3.0 was not meant for production use (eg io library was pure python).

yiedyie2• 13 years ago

This will make some people to switch to other distributions, because in some cases making your software compatible with Python 3 is harder than changing distributions.

shawnz• 13 years ago

Why isn't installing Python 2 an option?

yiedyie2• 13 years ago

The system might use python for other task, making python 2. as default may bring issues. I remember that installing python 3 on a version of ubuntu an making a symbolic link /usr/bin/python to python3 wrecked apt and the updating system.

reidrac• 13 years ago

I don't think so because it is really easy to install Python 2 and have both versions installed.

I'm already doing that, the difference is that "python" for me is Python 2 and I have to run "python3" to use Python 3. Other than that, I can't see any problem. You can install packages for both versions, the distros usually add a number (ie. python-django, python3-django).

keypusher• 13 years ago

That will still be the case. As the proposal makes clear, this will make the system tools use Python3, but "python" (/usr/bin/python) will still point to python2.7

AdamN• 13 years ago

Let those people go

mercnet• 13 years ago

On Arch, the only issue I run into is typing python2/pip2 vs python/pip. The transition was smooth and nothing broke for me.

maxk42• 13 years ago

That may be so, but this is the sort of mentality that was responsible for IE6 being maintained after the release of IE8.

In the long run, switching to python3 will be better.

yuvadam• 13 years ago

This is a good move towards real adoption of Python 3, and doesn't have as dire consequences as it seems.

Distros that use Python 3 by default (such as Arch and Gentoo) still allow for Python 2 to work side-by-side with Python 3. Proper separation using virtualenvs works seamlessly, and there's no problem at all to work simultaneously on Py2 and Py3 projects.

sentenza• 13 years ago

When I read the headline, my first thought was: "Well, _I_ alread switched over some time ago."

Then after reading your comment, I remembered that my complete switchover was triggered by the default version switch in my primary machine's distro (Arch).

So indeed, these things do matter for real-world adoption of Python 3.

JulianWasTaken2• 13 years ago

This is untrue about Arch, but true about Gentoo and seemingly will be about Fedora. Your experience with "Py3 default distros" has a bit to do with what version `python` points to. You certainly can get by with virtualenv all over and / or setuptools rewriting shebang lines but it's less convenient.

From the two sections in here it appears that Fedora will stick with `python` pointing to Py2, so that's good news.

viraptor• 13 years ago

What's untrue about Arch? /usr/bin/python is python3 by default in there.

stefantalpalaru• 13 years ago

Gentoo lets you choose the python dialect/version with "eselect python".

Arch switched to python3 as the default "/usr/bin/python" with no way to change it because of their persistence on following the upstream. They payed the price by having to hunt down and modify all the python2 scripts.

phaer• 13 years ago

Well, "modify" could mean to just add !#/usr/bin/python2 to the top, right?

thomasjames• 13 years ago

The one downside to this in terms of this move increasing adoptions is that RHEL 7 will be based on Fedora 19 not Fedora 20 and subsequent releases. If Python 3 managed to be default on RHEL/CentOS and the like, that would have a much broader impact.

ushi• 13 years ago

I think it is a little bit silly for a distro that claims to be bleeding edge... (freedom. friends. features. FIRST.)

broodbucket• 13 years ago

Fedora is very much bleeding edge as far as stable distributions with set release cycles goes. First in the category of Ubuntu/Debian/openSUSE, not in the category of Arch/Gentoo.

drill_sarge2• 13 years ago

The interesting thing is of course: >DNF is the default package manager instead of Yum, which only works with Python 2

Otherwise no big news, since all other major distros are switching to default python 3 too.

qznc3• 13 years ago

DNF is a fork of Yum, so not that big news either.

drill_sarge2• 13 years ago

This whole thing is no _big_ news at at all. I wonder what they define with "scope". If they are talking about 21+22 thats around ~12 months ahead, so even less big news.

sigzero• 13 years ago

Great news!

thearn4• 13 years ago

A good way to get folks to make the switch.

I just wish Python 3 didn't benchmark so much slower than Python 2 in some of my use cases (though I still aim for compatibility with it).

Couple of relevant search results:

http://stackoverflow.com/questions/14911122/same-code-slower...

http://pythonadventures.wordpress.com/2013/08/15/python-3-is...

Has anyone else experienced this?

bloodearnest• 13 years ago

I think readlines() is slower in python 3 due to unicode decoding. Python 2 did no decoding, readlines() returns python 2's str type, just bytes. You'd have to decode yourself (or decode the whole file in open()). Python 3 readlines() does decoding into unicode code points by default.

Do a benchmark after the file has been opened with an explicit encoding, to see if I'm right. If the files already been decoded, there shouldn't be as big a difference.

throwaway91012• 13 years ago

Codechef appears to use Python 3.1.2 for "Python3", which is pretty old (March 21st, 2010) and predates some significant performance improvements in Python3[0].

[0]: E.g., 3.3 adds a more efficient encoding for ASCII-subset unicode strings: http://docs.python.org/3/whatsnew/3.3.html#performance-and-r...

throwaway91012• 13 years ago

Fedora 22 is ... 3 releases out? So we're talking about 12-18 months depending on how soon F20 is due to be released. Still, I'm surprised, and I've been a Fedora contributor since FC5.

simonh• 13 years ago

A lot of the comments here seem to me to be based on a confusion between Python as a development tool for users and developers, and Python as a base operating system component. These are two very different roles that the language fills.

IMHO confusing these roles and providing, or expecting one install of a language to fit both simultaneously has been something that's irritated me about Unix-like OSes for a long time, much as I love them.

Yes I know there are plenty of tools for installing dev versions of tools side by side with the system components. IMHO doing so should be the default assumption unless you really are developing system scripts or scripts that you explicitly expect to be limited in scope to that OS.

memracom• 13 years ago

I try to never use any distro installed Python or libraries when developing Python software. In fact, I even went to the trouble of creating a self-contained Python build that had no dependencies whatsoever on distro-installed libraries. That way I have even more control over the foundation of my applications than you get with virtualenv.

Next time I do some Python development (other than system admin scripts) I will be using Python 3.4. And I will likely also create a self-contained build of that as well.

jessaustin3• 13 years ago

I wonder if this has any effect on the plans for CentOS? Somehow I suspect there would be more wailing and gnashing of teeth from that user community. (Not a criticism, just an appraisal of what CentOS folks do and how they're set up.)

stock_toaster2• 13 years ago

CentOS still has python2.6 as the default. Several people I know who use CentOS with python just build their own python2.7 anyway -- at $dayjob, I build python2.7 and package it up with fpm[1] and drop it in our internal repo.

[1] https://github.com/jordansissel/fpm

jessaustin3• 13 years ago

Great link to fpm! I'm definitely going to check that out.

shuzchen2• 13 years ago

CentOS is just a rebranding of RHEL, which uses Fedora as upstream source. Basically when they start a new version of RHEL, they pick some Fedora version as a starting point, freeze things and make everything enterprise ready.

So, yes, this likely means some future version of RHEL (and thus derivatives like CentOS and Scientific Linux) will also make the "switch" over to python3. Considering the turnaround time for RHEL versions (and how Fedora is still slow on the uptake of python3), I wouldn't expect this to happen anytime soon though.

fulafel2• 13 years ago

centos users had to live with python 2.4 until recently...

jessaustin3• 13 years ago

Wow. I was asking honestly, as a user of CentOS.

oddshocks• 13 years ago

"DNF is the default package manager instead of Yum, which only works with Python 2"

This will be interesting.

puppetmaster3• 13 years ago

This is not news. All distros will. News would be: Fedora, that normally is late, has switched to Python 3 a year after others.

pippy• 13 years ago

I'm still using python 2.7 because many of my libraries require it, such as wxwidgets and pygame.

jamesgeck0• 13 years ago

PyGame actually does mostly support Python 3. Their binaries seem to be a little old, though.

cafard• 13 years ago

I understand the ressons for moving to Python 3. But I'm glad that most of my Python code runs on Windows.

mistercow• 13 years ago

Is there a good reason that the Python project didn't just adopt a new command name and file extension for Python 3? It seems like that would have made the migration a lot less painful.

Fedora Linux will switch to Python 3 by default

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