This script, often essentially a rename of the concept of an "install.py," was the gatekeeper. It would check your system for a C compiler, look for dependencies, and then physically move files into your Python's site-packages folder. The Evolution: From Scripts to Tools

As projects grew more complex, setup.py evolved into setuptools . However, running a raw .py file for installation had risks. It executed arbitrary code on your machine with full permissions—a "long story" that often ended in broken system Python installations.

While largely deprecated for general libraries, you will still find install.py in specific, specialized corners of the tech world: