Python 3.4+Async programmingterm

asyncio.Event

synchronization

A flag for signalling between tasks: some wait with await event.wait(), another calls event.set(), and all waiters wake up at once.

Syntax

event = asyncio.Event(); await event.wait(); event.set(); event.clear()

After set() the flag stays raised: every later wait() returns immediately until you call clear() — an Event is a state, not a one-shot nudge. set() is a plain method, not a coroutine, so it is not awaited. Do not call set() from another thread — this is not threading.Event; use loop.call_soon_threadsafe(event.set).

Examples

import asyncio
async def waiter(name, event):
    await event.wait()
    print(name, 'проснулся')
async def main():
    event = asyncio.Event()
    tasks = [asyncio.create_task(waiter(n, event)) for n in ('a', 'b')]
    await asyncio.sleep(0.01)
    event.set()
    await asyncio.gather(*tasks)  # → a проснулся / b проснулся
    print(event.is_set())  # → True — флаг остался поднят
asyncio.run(main())

See also

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