python runtime_error ai_generated true

RuntimeError: Event loop is closed

ID: python/event-loop-closed-runtimeerror

Also available as: JSON · Markdown · 中文
80%Fix Rate
88%Confidence
0Evidence
2024-03-12First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.8+ active — — —
3.10+ active — — —
3.12 active — — —

Root Cause

An asyncio coroutine or aiohttp session is reused after the event loop that created it has been closed. Common when calling asyncio.run() multiple times, or when a ClientSession is created outside the loop and used inside a different asyncio.run() call. The underlying transport/socket is bound to a now-dead loop.

generic

中文

在创建它的 asyncio 事件循环已关闭后，仍复用了协程或 aiohttp 会话。常见于多次调用 asyncio.run()，或在循环外创建 ClientSession 却在另一次 asyncio.run() 内使用。底层 transport/socket 绑定在已失效的循环上。

Workarounds

  1. 95% success 
    async def main():
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as r:
            return await r.text()

asyncio.run(main())  # session lives and dies inside this loop
  2. 85% success 
    import asyncio
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
try:
    loop.run_until_complete(main())
finally:
    loop.run_until_complete(loop.shutdown_asyncgens())
    loop.close()

Dead Ends

Common approaches that don't work:

  1. 90% fail

    Silencing the exception leaves the coroutine unfinished and leaks resources; the next call fails differently or hangs.

  2. 95% fail

    A closed loop cannot be restarted; run_until_complete raises RuntimeError immediately.

  3. 85% fail

    Policy changes do not resurrect a closed loop; the error is lifecycle, not platform.