Good point. I use gevent and now switching back to eventlet. But that is a different post perhaps.

Not only do you get more threads with greenlet you also don't have to worry about a whole class of synchronization side-effects since a greenlet will only switch contexts on an IO operation. (Now some might argue that is bad since you could be calling a function and not know what happens in side or what might happen in the future so you should lock anyway).