Never Add Packages to the System Python

If you use pip, it is all too easy to accidentally install packages to your system Python (just forget to activate a virtual environment before running pip install).

Messing with your system Python is not a good idea (and is likely to cause conflicts between your projects), but you can protect yourself from accidentally doing this by setting the environment variable PIP_REQUIRE_VIRTUALENV. For example, in your .bash_profile, include:

export PIP_REQUIRE_VIRTUALENV=true

This will make the installation fail unless you have an active virtual environment.

(My real recommendation would be to use uv instead to handle your project dependencies—it enforces this by default.)