On 8 March 2016 at 22:00, Steve Dower steve.dower@python.org wrote:
"First installed" is a very difficult proposition, especially if you want versions of Python pre-3.6 to participate. "Last installed" is slightly better, though not easy to do without triggering systems that detect corrupted installations.
Also, any dependency on installation order gets *very* messy if someone installs and uninstalls various versions. What does the default become if I uninstall the version that was previously the first (or last) installed? Would we need to keep details of precisely when everything was installed?
Personally I think "latest version" is the best default (compared to the current "latest 2.x version"), so I'm +1 on removing the assumption that "PY_PYTHON" is "2" by default.
Latest version has the additional advantage of being essentially the current behaviour, just with the special case of "but prefer Python 2 over Python 3 if both are present" removed. (Note that technically the current rule is not simply "latest 2.x version", as if the user only has Python 3 installed, the latest 3.x version is used).
The only other option I can think of is "use the one the user selected as the default Python (i.e., introspect the association for ".py" files) but even then we need a default default (!) for people who don't select any default Python. It's also messy to implement. And it's a bigger change from current behaviour.
Users can change their own default with any of the mechanisms described at https://docs.python.org/3/using/windows.html#customization
Absolutely. This should *only* apply when there is no user customisation - and it needs no further configurability, because the current methods are perfectly sufficient.
Paul