[Python] Python Asyncio Condition: Why DeadLock appears?

I learn python asyncio and now struggling with Conditions. I wrote a simple code:

import asyncio


async def monitor(condition: asyncio.Condition):
current_task_name = asyncio.current_task().get_name()
print(f'Current task {current_task_name} started')
async with condition:
await condition.wait()
print(f'Condition lock released for task {current_task_name}, start doing smthg')
await asyncio.sleep(2)
print(f'Current task {current_task_name} finished')


async def setter(condition: asyncio.Condition):
print(f'Setter starts')
async with condition:
await asyncio.sleep(1)
condition.notify_all() # Пробуждаем все задачи
print('Setter finished')
print('Setter unlocked')


async def main():
cond = asyncio.Condition()
async with asyncio.TaskGroup() as tg:
tg.create_task(setter(cond))
[tg.create_task(monitor(cond)) for _ in range(3)]
# tg.create_task(setter(cond))


asyncio.run(main())


But the code catches a DeadLock after Setter unlocked message. I cant realise why. But if I swap task creation order in main and create monitor tasks prior to creation setter task- all good.

please, I am a very new in asyncio, so please, in simple words...

Continue reading...