gevent
Coroutine-based concurrency library for Python
... license. API that re-uses concepts from the Python standard library (for examples there are events and queues). Cooperative DNS queries performed through a threadpool, dnspython, or c-ares. Monkey patching utility to get 3rd party modules to become cooperative. When monkey patching, it is recommended to do so as early as possible in the lifetime of the process. If possible, monkey patching should be the first lines executed.