Twisted in Python is a very popular and very powerful event-driven networking engine that can be used for a huge range of different projects such as web servers, mail clients, sub-systems, and more.
Twisted is an amalgamation of both high- and low-level APIs that can be effectively utilized to create very powerful, elegant programs without masses of boilerplate code. It is both asynchronous and event-based by design and could be compared to the asyncio module as a more fully fleshed out older sibling.
If you are interested in learning far more on the Twisted framework then I fully recommend Twisted Network Programming Essentials, 2nd Edition, by Abe Fettig and Jessica McKellar
