Python 3.14中asyncio/asyncpg出现Event loop closed错误的解决方法

问题重现 #

你在Python 3.14中运行以下代码时触发RuntimeError: Event loop is closed错误：

import asyncio
import asyncpg

def adapted_async():
    conn = asyncio.run(asyncpg.connect(database='async_test'))
    asyncio.run(conn.close())
          
if __name__ == "__main__":
    adapted_async()

完整报错堆栈：

RuntimeError: Task <Task pending name='Task-5' coro=<Connection.close() running at /Users/Me/Documents/Dev/async_test/.venv/lib/python3.14/site-packages/asyncpg/connection.py:1513> cb=[_run_until_complete_cb() at /opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/base_events.py:181]> got Future <Future pending cb=[BaseProtocol._on_waiter_completed()]> attached to a different loop

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/xof/Documents/Dev/async_test/x.py", line 10, in <module>
    adapted_async()
    ~~~~~~~~~~~~~^^
  File "/Users/xof/Documents/Dev/async_test/x.py", line 6, in adapted_async
    asyncio.run(conn.close())
    ~~~~~~~~~~~^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/runners.py", line 204, in run
    return runner.run(main)
           ~~~~~~~~~~^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/runners.py", line 127, in run
    return self._loop.run_until_complete(task)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/base_events.py", line 719, in run_until_complete
    return future.result()
           ~~~~~~~~~~~~~^^
  File "/Users/xof/Documents/Dev/async_test/.venv/lib/python3.14/site-packages/asyncpg/connection.py", line 1513, in close
    await self._protocol.close(timeout)
  File "asyncpg/protocol/protocol.pyx", line 640, in close
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/selector_events.py", line 830, in abort
    self._force_close(None)
    ~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/selector_events.py", line 902, in _force_close
    self._loop.call_soon(self._call_connection_lost, exc)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/base_events.py", line 827, in call_soon
    self._check_closed()
    ~~~~~~~~~~~~~~~~~~^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.14/lib/python3.14/asyncio/base_events.py", line 550, in _check_closed
    raise RuntimeError('Event loop is closed')

错误原因 #

你对asyncio.run()的理解有偏差：虽然每次调用asyncio.run()确实会创建新事件循环，但它在协程运行结束后会自动关闭这个循环。

第一次调用asyncio.run(asyncpg.connect(...))时，创建的数据库连接conn会绑定到这次的事件循环上；当该调用结束，这个循环被关闭。第二次调用asyncio.run(conn.close())会创建新的事件循环，但conn的底层网络协议仍然绑定在已关闭的旧循环上，执行close()时会尝试调用旧循环的方法，最终触发“事件循环已关闭”的错误。

正确实现方式 #

方案一：单协程包裹所有异步操作（推荐） #

将连接创建、业务操作、连接关闭放在同一个协程中，只调用一次asyncio.run()：

import asyncio
import asyncpg

async def main():
    # 创建连接
    conn = await asyncpg.connect(database='async_test')
    # 这里可以添加数据库操作逻辑
    # 关闭连接
    await conn.close()

if __name__ == "__main__":
    asyncio.run(main())

方案二：手动管理事件循环（不推荐，仅作演示） #

如果必须拆分操作，需确保所有异步操作都在同一个事件循环中执行：

import asyncio
import asyncpg

def adapted_async():
    # 创建事件循环
    loop = asyncio.new_event_loop()
    try:
        # 在同一循环中执行连接创建和关闭
        conn = loop.run_until_complete(asyncpg.connect(database='async_test'))
        loop.run_until_complete(conn.close())
    finally:
        # 手动关闭循环
        loop.close()

if __name__ == "__main__":
    adapted_async()

内容的提问来源于stack exchange，提问作者Christophe