On Thu, Sep 1, 2016 at 7:44 AM, Nick Coghlan <ncoghlan@gmail.com> wrote:

The ideal point we'd like to get to is one where all distro provided
scripts actually have the appropriate major version in their shebang
lines, and the unqualifed "python" is something along the lines of a
user-configurable launcher, akin to the "py" launcher for Windows:
https://docs.python.org/3/using/windows.html#python-launcher-for-windows
(see https://www.python.org/dev/peps/pep-0397/ for more details on
that)

While I see some benefit to something like this and could see use cases for including it in the shebang, it would be overkill for "/usr/bin/python". Windows needs something like that because it doesn't support symlinks.

Let's stop trying to reinvent the wheel. There is already a system for handling this, alternatives, which is used by other languages and included in a minimal Fedora install. It would only require adding to the %post and %postun scripts in the spec file and allows very easy testing to see what breaks when changing the default. When we are ready to change the default, only one value needs to be changed. And most importantly, it gives the end-user an easy way to change their system-wide default either from python 2 to 3 or when running a pre-release version of 3.x in parallel.

Avram