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

femtorun
1.999.999

This version was deleted from PyPI around 2023-12-16. Installing fails with:
$ pip3 install femtorun==1.999.999 ERROR: Could not find a version that satisfies the requirement femtorun==1.999.999
View other deleted versions of femtorun

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/2023-12-15/ \ femtorun==1.999.999
Sign up for StableBuild to get an API key (it's free and takes <60 seconds!)

Or, download files manually

And install manually via pip:
femtorun-1.999.999-py3-none-any.whl (13.6KB)