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

arts
2023.9.5.1

This version was deleted from PyPI around 2023-10-29. Installing fails with:
$ pip3 install arts==2023.9.5.1 ERROR: Could not find a version that satisfies the requirement arts==2023.9.5.1
View other deleted versions of arts

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/2023-10-28/ \ arts==2023.9.5.1
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Or, download files manually

And install manually via pip:
arts-2023.9.5.1-py2.py3-none-any.whl (197.1KB)
arts-2023.9.5.1.tar.gz (124.2KB)