Difference between gevent.sleep() and time.sleep() in Python

Question

What is the difference between gevent.sleep() and time.sleep() in Python? When to gevent.sleep() and time.sleep()?

Answer 1

(Recall that gevent runs multiple greenlets on a single Python thread, multiplexing them cooperatively to perform cooperative multitasking, switching amongst them as they would block for IO.)

gevent.sleep() will yield the current greenlet to the gevent hub, allowing other greenlets to run. time.sleep() will not yield to the hub; it will simply suspend the entire current thread and all greenlets that might like to run on it.

On the other hand, time.sleep will release the Python GIL and allow other Python threads the opportunity to run (but still blocking all greenlets on the calling thread), whereas gevent.sleep does not release the GIL (unless there are no other greenlets ready to run on the calling thread).

If you have monkey-patched your program (early enough) using gevent.monkey.patch_all(), then time.sleep simply becomes an alias for gevent.sleep and there is no difference.

In a program using gevent, monkey patching or explicitly using gevent.sleep is generally recommended instead of time.sleep, otherwise you won't achieve the full benefits of cooperative greenlets.

More details are provided in the introductory gevent documentation, specifically the sections on the event loop, cooperative multitasking, and pseudothreads (greenlets).