In which rogue call_soons starve cooperating callbacks.

clog_the_event_loop.py

import asyncio
import time

loop = asyncio.get_event_loop()

async def go(sleep):
    await asyncio.sleep(sleep)
    print('I slept', sleep, 'seconds')

def clog(sleep):
    time.sleep(sleep)
    print('I clogged', sleep, 'seconds')

loop.call_at(loop.time() + 0.3, lambda: print('here I am'))
loop.create_task(go(1))
loop.create_task(go(2))
loop.create_task(go(3))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.call_soon(lambda: clog(1))
loop.run_forever()

I don't know what you're trying to prove here. Of course the event loop is unavailable when a coroutine calls time.sleep().