Modern Python Standard Library Cookbook

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We already know that the most important benefit of coroutines is that the event loop is able to pause their execution while they are waiting for I/O operations to let other coroutines proceed. While there is currently no built-in implementation of HTTP protocol with support for coroutines, it's easy enough to roll out a back version to reproduce our example of downloading a website concurrently to track how long it's taking.

As for the ThreadPool example, we will need the wait_until function that will wait for any given predicate to be true:

async def wait_until(predicate): """Waits until the given predicate returns True""" import time seconds = 0 while not predicate(): print('Waiting...') await asyncio.sleep(1) seconds += ...