Cornice provides helpers to build & document REST-ish Web Services with Pyramid, with decent default behaviors. It takes care of following the HTTP specification in an automated way where possible.
Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. By using non-blocking network I/O, Tornado can scale to tens of thousands of open connections, making it ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user.