@cryptoxic I usually use pipx for things where it's basically an implementation detail that it's written in Python. `isort`, `black`, `virtualenv`, `build`, `tox` and any of those sorts of command line tools could be written in any language and be just as useful, but `pipx` is a convenient way to install them (`virtualenv` is a bit of a weird one in that respect because it defaults to using the Python it's installed with as the runner).

That said, each of my projects has coding standards to be enforced, and I want to enforce those irrespective of what is installed in any global system (e.g. on CI, or on a random contributor's computer), so that stuff all goes into `tox`.

I use `virtualenv` to create an isolated environment in which to either install libraries to play around with or to execute little scripts that have some dependencies.