New submission from Alexander Greckov :
Hi! I've met strange behaviour related to the coroutine execution. Probably
it's somehow related to the asyncio.Queue get() method. I have the following
lines of code:
class WeightSource:
def __init__(self):
self._queue = asyncio.Queue(maxsize=1)
def __aiter__(self):
return self
async def __anext__(self):
return await self._queue.get()
async def _preconfigure(app: web.Application) -> None:
setup_db()
# asyncio.create_task(WeightSource.listen_scales('/dev/ttyACM0', 9600)
asyncio.create_task(handle_weight_event_creation()) # coroutine prints
WEIGHT
await create_track_tasks()
async def create_track_tasks():
asyncio.create_task(track_scales_availability())
asyncio.create_task(track_crm_availability())
async def track_scales_availability():
async for weight in WeightSource():
print(weight)
When I'm trying to run _preconfigure coroutine (automatically started by
aiohttp), i see the message: ERROR:asyncio:Task was destroyed but it is
pending. The strange things two:
The process and loop remains alive (so by the logic error should be not shown)
and the second thing is when I export PYTHONASYNCIODEBUG=1 everything works
well without any error.
On unset this variable the error returns. When I don't use asyncio.Queue and
just place asyncio.sleep(), coroutine doesn't fall. Error happens inside the
`async for weight in WeightSource()` statement. Why PYTHONASYNCIODEBUG changes
behaviour?
--
components: asyncio
files: output.txt
messages: 382307
nosy: Alexander-Greckov, asvetlov, yselivanov
priority: normal
severity: normal
status: open
title: AsyncIO strange behaviour
type: behavior
versions: Python 3.7
Added file: https://bugs.python.org/file49644/output.txt
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<https://bugs.python.org/issue42538>
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