You'll also be happy to learn that there's an issue open to deprecate them: https://github.com/python/cpython/issues/78125

It's been open since 2018 though. You might find it worth a read.

Yup, subscribed to that one already!

I searched all my machines and could only find simple ones, all related to some legacy crud for setuptools, one of which was a way to get eggs (which nobody should be using these days) to work.

They're barely a thing these days and mostly a relic from before the end of the Great Setuptools Stagnation and the site package all but discourages their use.

It shows that the language is highly dynamic and you can patch anything? The .pth mechanism allows the party controlling the Python installation (site) to run some init code before any user code, basically an rc mechanism. Nothing more, nothing radical. Maybe you’re unhappy with the dynamism, in which case your complaint is misplaced.

In this case it prevents someone using PYTHONPATH to alter or override the order that modules are loaded. Hard to justify that.

Again, the blame for that is at the feet of those who wrote the .pth file, not the mechanism itself.