I really don't understand virtual environments!
Here is a diff of `pip freeze`
base Arch install <---> new virtual environment
When I looked at the requirements output inside of the venv, I just assumed this was the same output as the non-venv (with the exception of the one pip package I installed, `python-magic`). The diff file shows there are a lot more differences than I realized.
That said, Numpy is installed, so I'm not sure about that problem.
But this is more complicated than I first imagined--and maybe easier to fix, too!