python runtime_error ai_generated true

RuntimeError: Task <Task pending name='Task-1' coro=<foo()>> got Future <Future pending> attached to a different loop

ID: python/asyncio-task-got-future-different-loop

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-05-02First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.8 active — — —
3.9 active — — —
3.10 active — — —
3.11 active — — —
3.12 active — — —

Root Cause

A coroutine created under one event loop is awaited under another loop, so the Future it holds belongs to a different loop than the Task waiting on it.

generic

中文

在一个事件循环下创建的协程在另一个循环中被 await，导致其持有的 Future 与等待它的 Task 属于不同的事件循环。

Workarounds

  1. 90% success 
    async def main():
    # session created inside the loop that will use it
    async with aiohttp.ClientSession() as session:
        await session.get(url)

asyncio.run(main())
  2. 85% success 
    future = asyncio.run_coroutine_threadsafe(coro(), target_loop)
result = future.result(timeout=10)

Dead Ends

Common approaches that don't work:

  1. 75% fail

    get_event_loop() can return the same stale loop or raise DeprecationWarning in newer versions; it does not reconcile two loops.

  2. 90% fail

    Sleeping does not migrate a Future between loops; the ownership mismatch remains.