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/
"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-...
Welcome to the real world.
In the case of Python 3, a neat thing library developers can do is write code that is both valid for Python 2 and Python 3. The six[0] library is a wrapper for making code compatible with both versions. There are tools like 2to3[1] and 3to2[2] that convert code from one version to another. They're not perfect but do catch the most common differences. Such things help with making the change.
However it is the availability (or more exactly lack of) of famous and widely used libraries that hinder or speed up the adoption. For example, Django recently started offering a Python 3 version[0]. Numpy and Scipy support it since around 2011 only.
0: http://pythonhosted.org/six
1: http://docs.python.org/2/library/2to3.html
2: https://wiki.python.org/moin/3to2
3: "Porting to Python 3" htthttp://pythonhosted.org/sixps://docs.djangoproject.com/en/de...
>Django 1.5 is the first version of Django to support Python 3. The same code runs both on Python 2 (≥ 2.6.5) and Python 3 (≥ 3.2), thanks to the six compatibility layer.
"Django's future, and Python 3" https://www.djangoproject.com/weblog/2012/mar/13/py3k/
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.
At least Python has a sane versioning scheme, where breaking compatibility increments the major version number or is a bug.
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.
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.
python 3.2.5 there (and not so later) by default and you can run oldest versions in parallel also
For ubuntu actual is window manager and good alternative desktop with usability, for Fedora maybe C development, for gentoo it is portage of course and their package manager powered by python.