For some reason, adoption has been really slow so far; it is disappointing to see so many beginners pick Python 2 over 3. I believe that even MIT and Coursera teach Python 2.
The only reason I've used Python 3 at all was because of project involving blender. I needed to do in-memory JPEG compression for quickly streaming images from the game engine. In Python 2, this is a couple lines of code using PIL. Instead, I ended up having to write my own pyjpeg module that provided a ctypes interface to a custom libjpeg-based compression library. I'm proud of the result, but the aggravation and frustration that entailed has removed any desire I have to move to Python 3.
Thanks for the Pillow link, btw. I was unaware of it.
The good news is that adoption should pick up very quickly after this fall. Python 3.3 will make it easier to port Python 2 projects and provide more incentives to upgrade. There's also nearly a critical percentage of major packages ported, and Django (which is still on Python 2, and is a deal breaker for many people) will have experimental support for versions up to 3.3.
I expect that by this time next year, the default for most new projects will be Python 3.
That's basically 90% of the time taken right there, since we had to do it one Python version at a time, giving people warnings that we'd be dropping support for 2.3, then 2.4, etc. so they'd be able to migrate up to a newer Python.
I think now that 2.7 is the last we will start to see a bit more migrate.
Edit: I didn't mean they aren't shipping 3.0, but that the default is still 2.7.x
The fact is that almost every major distro is shipping Python 3, and often has been for several releases/years: Fedora, Ubuntu, openSUSE, Debian, Gentoo, ArchLinux ... and many of these also have anywhere from dozens to hundreds of Python 3 libraries packaged.
If you mean that /usr/bin/python still points to Python 2 on most of these (in fact all of them except for ArchLinux): True, and that is unlikely to change, possibly never. It's my understanding that this is in keeping with upstream's wishes (from discussions on python-devel and python-porting): bin/python is to remain Python 2 with python3 being the right way to run the Python 3 interpreter.
The consensus from Python list discussions like "Shebang lines for Python 3" and "Support the /usr/bin/python2 symlink upstream" seemed to be that /usr/bin/python is to remain Python 2 indefinitely and that newly-written scripts should call python2 or python3 explicitly. If I recall right Guido's stance was the latter, but leaving plain python up to distros.
There's also PEP 394: http://www.python.org/dev/peps/pep-0394/
This is further cemented, if you will, by the new Windows launcher in 3.3 that extends shebang support to that platform and supports the same mappings.
That said, one of the KDE applications I maintain contains a fair amount of Python code, and since I consider Python 3 to be a much nicer language, it of course runs fine on 3.x. And purely from an emotional POV the fact that the Arch packages get to install those scripts without their usual sed call to replace "python" with "python2" does bring a smile to my face.
For someone just starting out with python (on linux anyways) that means they are probably going to fire up that interpreter first.
I was wondering myself actually if any of the distros would switch to 3.0. I think a lot of packages would break if that were to happen.
As you've said, Arch has already switched but their package release isn't really typical for most distros.
I think that's probably a too aggressive schedule to actually keep, but here's hoping.
Linux developers and sysadmins are lazy by default (with good reasons: they have a lot to do). To make them get off their arses, you have to switch defaults and scream loudly when stuff breaks, otherwise they'll never bother.
If the problem is that it will break package xyz that is so old and completely unmaintained that nobody can fix it, well, it's a good reason to drop a zombie package. If your code depends on a zombie package, things would have broken down sooner or later anyway.
Python2 is still in base-devel, but /usr/bin/python symlinks to python3, not python2.