[nerpderp82]

I have a default Python env that my shell sources for every login shell. I can deactivate it and activate different envs on a per project basis.

That default Python env means I don't ever modify the system python for any reason. I type `python` and I get my own Python3 from the base.env

If you use homebrew, there are two settings that help keep your old python binaries around so that venvs that reference those old envs don't break.

HOMEBREW_NO_CLEANUP_FORMULAE, this takes a lists of packages to not cleanup

HOMEBREW_NO_INSTALL_CLEANUP, prevents old packages from getting removed