Python 3.4+until 3.16Async programmingfunction

asyncio.set_event_loop_policy()

event loop

Deprecated: replaces the global event loop policy; deprecated since 3.14 with removal in 3.16. Use loop_factory of asyncio.run() and Runner instead.

Syntax

asyncio.set_event_loop_policy(policy)

The classic old recipe is set_event_loop_policy(uvloop.EventLoopPolicy()) or WindowsSelectorEventLoopPolicy() for libraries that fail under Proactor. The swap is global: it affects the whole process, other libraries and tests included. Today the same is done locally: asyncio.run(main(), loop_factory=uvloop.new_event_loop). set_event_loop_policy(None) restores the default policy.

Examples

# Python 3.12+
import asyncio
async def main():
    await asyncio.sleep(0.01)
    return 'ок'
# вместо set_event_loop_policy(...) — цикл для одного запуска
print(asyncio.run(main(), loop_factory=asyncio.new_event_loop))  # → ок

import asyncio
import warnings
with warnings.catch_warnings():
    warnings.simplefilter('ignore', DeprecationWarning)  # с 3.14 вызов устарел
    asyncio.set_event_loop_policy(None)  # None — политика по умолчанию
print(asyncio.run(asyncio.sleep(0.01, result='ок')))  # → ок

# Python 3.16+
import asyncio
async def main():
    await asyncio.sleep(0)
    return 'ок'
# вместо set_event_loop_policy(...): один цикл на несколько запусков
with asyncio.Runner(loop_factory=asyncio.EventLoop) as runner:
    print(runner.run(main()), runner.run(main()))   # → ок ок

asyncio.set_event_loop_policy()

Syntax

Examples

See also