python runtime_error ai_generated true

RuntimeError: <asyncio.locks.Semaphore object at 0x...> is bound to a different event loop

ID: python/asyncio-semaphore-bound-in-different-loop

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-12-03First Seen

Version Compatibility

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

Root Cause

An asyncio synchronization primitive (Semaphore, Lock, Event, Queue) was created under one loop and used under another, common when module-level primitives are reused across asyncio.run() calls.

generic

中文

在某个事件循环下创建的 asyncio 同步原语（Semaphore、Lock、Event、Queue）被另一个循环使用，常见于跨 asyncio.run() 调用复用模块级原语。

Workarounds

  1. 95% success 
    async def main():
    sem = asyncio.Semaphore(10)  # created inside the loop
    await run_all(sem)

asyncio.run(main())
  2. 90% success 
    loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
loop.run_until_complete(main())  # reuse loop; do not call asyncio.run() repeatedly

Dead Ends

Common approaches that don't work:

  1. 85% fail

    Private attribute hack; the semaphore's internal waiters still reference the old loop.

  2. 80% fail

    The primitive is still bound to its original loop; new loop does not fix it.