You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

pyosys
0.55.46

This version was deleted from PyPI around 2025-08-05. Installing fails with:
$ pip3 install pyosys==0.55.46 ERROR: Could not find a version that satisfies the requirement pyosys==0.55.46

Install through StableBuild

You can install this package from StableBuild's PyPI snapshots from before the version was deleted:
pip3 install \ -i https://YOUR_API_KEY.pypimirror.stablebuild.com/2025-08-04/ \ pyosys==0.55.46
Sign up for StableBuild to get an API key (it's free and takes <60 seconds!)