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

yyperf
0.6.10.dev123

This version was deleted from PyPI around 2023-11-21. Installing fails with:
$ pip3 install yyperf==0.6.10.dev123 ERROR: Could not find a version that satisfies the requirement yyperf==0.6.10.dev123
View other deleted versions of yyperf

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/2023-11-20/ \ yyperf==0.6.10.dev123
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:
yyperf-0.6.10.dev123-py3-none-any.whl (17.9MB)
yyperf-0.6.10.dev123.tar.gz (16.5MB)