Twisted
Event-driven networking engine written in Python
...It includes modules for many different purposes. Twisted supports all major system event loops, select (all platforms), poll (most POSIX platforms), epoll (Linux), kqueue (FreeBSD, macOS), IOCP (Windows), and various GUI event loops (GTK+2/3, Qt, wxWidgets). Third-party reactors can plug into Twisted, and provide support for additional event loops.