About 10 years ago, multi-armed bandits (and especially contextual bandits) were really important for optimization and business use cases.

But nowadays you hardly hear about it, despite optimization continuing to be a need. The only major open source library continues to be Vowpal Wabbit - and even that is not very robustly maintained or documented.

What are people doing for bandits or optimization needs nowadays? And what are some active, Python-centric, open-source libraries with a strong user community and stable code?