Python could do green threads (IO-base coroutines) for a long time -- see eventlet, gevent, even Twisted's inlineCallback pattern. There are probably others, there was even one based on "yields" as well.
Yap, I've used and shipped code based on eventlet. And you are right PyPy supports that as well. I have never tested it using PyPy. Perhaps one day. For large concurrency cases I would probably look at Erlang/Elixir though...
