pYsearch is used by Pywikibot for Yahoo! searches, and it was supported by Yahoo!.
However it contains a baked in hostname of http://search.yahooapis.com/ , which is the old service that was shut down in 2011.
In addition, it is an unmaintained package on pypi which requires fetching the tarball from sourceforge.net, which can cause build breakages whenever sourceforge.net has problems, such as T106062: Travis builds failing due to 403 downloading pYsearch from sourceforge.net.
Yahoo now offers Boss Search API, hosted at https://yboss.yahooapis.com/ , and there appear to be a few packages which provide that.
https://pypi.python.org/pypi/justsearch
https://pypi.python.org/pypi/yboss
https://pypi.python.org/pypi/YahooBoss-Python
However, using Boss Search incurs fees, so it is probably unsuitable for bot usage. Their pricing page goes to a Terms of Use page which doesnt appear to include pricing details. Boss Overview includes a link for Pricing, however that doesnt load anything at all.