`pipx` - install and run Python applications in isolated environments

pipx install PACKAGE  |  pipx list  |  pipx uninstall PACKAGE  |  pipx ensurepath

Options you will use

install PKG: Make a venv for PKG under ~/.local/share/pipx/venvs/PKG, pip-install it there, and symlink its apps (console scripts) into ~/.local/bin.
install --force PKG: Reinstall over an existing venv.
list: Installed applications, the Python each uses, and the apps each exposes.
uninstall PKG: Remove the venv and its symlinks.
ensurepath: Append ~/.local/bin to PATH in ~/.bashrc (takes effect in a new shell).
--version: Print the pipx version.

$ sudo apt install pipx

pipx itself comes from apt; apps go into your home, no sudo.

$ pipx install pytest

pytest and py.test in ~/.local/bin, isolated from every other tool.

pipx is for applications (things with a command). A library like requests has no apps: pipx refuses it - use pip in a venv.
The answer to "externally-managed-environment" for a CLI tool: one venv per tool, without managing it by hand.

Try pipx in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.