Issue
In the first example I am getting output
I expect here to be, but I can't say same about second example. Technically, in both example I have 3 tasks
(Just in second example, I am scheduling 2 coros
execution from main coro
) isn't it ? In second example, why Event loop
does not resume main() coro
in the same fashion as in first example ?
Example 1:
import time
import asyncio
async def coro1():
while True:
print('coro1()')
await asyncio.sleep(0.1) # yield ! Give control back to event loop, to start/resume another task !
async def coro2():
while True:
print('coro2()')
await asyncio.sleep(0.1) # yield ! Give control back to event loop, to start/resume another task !
async def main():
while True:
print('main()')
await asyncio.sleep(0.1) # yield ! Give control back to event loop, to start/resume another task !
if __name__ == '__main__':
loop = asyncio.get_event_loop()
main_task = loop.create_task(main())
task1 = loop.create_task(coro1()) # Schedule execution of coro !
task2 = loop.create_task(coro2()) # # Schedule execution of coro !
loop.run_until_complete(main_task)
loop.close()
Example 1 Output:
main()
coro1()
coro2()
main()
coro1()
coro2()
main()
coro1()
coro2()
Example 2:
import time
import asyncio
async def coro1():
while True:
print('coro1()')
await asyncio.sleep(0.1) # yield ! Give control back to event loop, to start/resume another task !
async def coro2():
while True:
print('coro2()')
await asyncio.sleep(0.1) # yield ! Give control back to event loop, to start/resume another task !
async def main():
loop = asyncio.get_running_loop()
task1 = loop.create_task(coro1()) # Schedule execution of coro from main !
task2 = loop.create_task(coro2()) # Schedule execution of coro from main !
while True:
print('main()')
await task1 # yield ! Give control back to event loop, to start/resume another task !
await task2 # yield ! Give control back to event loop, to start/resume another task !
if __name__ == '__main__':
loop = asyncio.get_event_loop()
main_task = loop.create_task(main())
loop.run_until_complete(main_task)
loop.close()
Example 2 output:
main()
coro1()
coro2()
coro1()
coro2()
coro1()
coro2()
Solution
None of your tasks ever complete, they'll all continue endlessly. In the first case, each task in itself only await
s asyncio.sleep
, which does complete; the code then continues with the next loop iteration.
In your second case, the main
task await
s the completion of the coro1()
task, before it will continue with its loop. Since coro1
never completes, it is indefinitely stuck at the await task1
line.
Answered By - deceze
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