I've upgraded debian thru the ages and /usr/bin/python defaulted to python2. Didn't need to install anything for that to happen, maybe if you installed debian from scratch
Another mistake in Py3 migration was keeping the interpreter name as python so when you had it in path you had a choice of new stuff breaking or old stuff breaking
> I've upgraded debian thru the ages and /usr/bin/python defaulted to python2
It was, in the past.
When python2.7 deprecated and removed in Debian testing, python ceased to exist as a command. You need to install these packages (python-is-python{2,3}) to get the python command and point to the correct interpreter you like.
This behavior is consistent in two Debian testing systems, installed 6 and 9 years ago, respectively.
> Another mistake in Py3 migration was keeping the interpreter name as python...
I installed python-as-python3 myself, after python2 disappeared from system to fix an oddball python3 script which bundled as a part of a bigger software package which is not in official repositories.
Maybe they have fixed it, but I didn't bother to check till now. I'm not even sure which program it was.
So, it was an addition to a clean system and didn't inadvertently directed python2 code to python3 interpreter.
Another mistake in Py3 migration was keeping the interpreter name as python so when you had it in path you had a choice of new stuff breaking or old stuff breaking