I really like tornado and websockets but keep in mind it gets dicey to scale on one box after you get to about 50 open connections at the same time on one box. You can do things to stretch that out but it's not the easiest thing. You also still have browser requirement issues. So it really depends on your use case polling, which is my least favorite method, is the most versatile method. It's easy to use flask for all of these issues. That said I'm a big fan of Tornado.