@mcc deadsnake work great in my experience, at least if what you need is a virtualenv.

my machine have no python in path. If I use python3, that's the ubuntu native one which is ok for quick access go a calculator. python3.x is a deadsnake python, or the native one for python3.9, which I use only to do -m venv.

Once I activate a venv, command python with no suffix is available so I don't use system wide python by accident.