You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.
lightning was reported malicious
OSV:MAL-2026-3201 - Malicious code in lightning (PyPI)

lightning
2.5.1.dev20250427

This version was deleted from PyPI around 2026-04-30. Installing fails with:
$ pip3 install lightning==2.5.1.dev20250427 ERROR: Could not find a version that satisfies the requirement lightning==2.5.1.dev20250427
View other deleted versions of lightning

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/2026-04-29/ \ lightning==2.5.1.dev20250427
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:
lightning-2.5.1.dev20250427-py3-none-any.whl (800.0KB)
lightning-2.5.1.dev20250427.tar.gz (614.0KB)