是否可以以某种方式自定义 QTabWidget？

Question

slx0009

Asked:2023-11-13 04:54:54 +0000 UTC2023-11-13 04:54:54 +0000 UTC 2023-11-13 04:54:54 +0000 UTC

为什么会出现 AttributeError: NoneType object has no attribute send 错误？

772

我了解 SQLAlchemy 和 FastAPI。我做了一个路由器并初始化了数据库，但由于某种原因，路由器的第一行出现错误：

INFO:     ::1:55018 - "GET /api/v1/places/ HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "C:\Users\dmm\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 772, in call_soon
    self._check_closed()
  File "C:\Users\dmm\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 519, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\uvicorn\protocols\http\httptools_impl.py", line 426, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\uvicorn\middleware\proxy_headers.py", line 84, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\fastapi\applications.py", line 1106, in __call__
    await super().__call__(scope, receive, send)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\applications.py", line 122, in __call__
    await self.middleware_stack(scope, receive, send)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\middleware\errors.py", line 184, in __call__
    raise exc
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\middleware\errors.py", line 162, in __call__
    await self.app(scope, receive, _send)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\middleware\exceptions.py", line 79, in __call__
    raise exc
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\middleware\exceptions.py", line 68, in __call__
    await self.app(scope, receive, sender)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\fastapi\middleware\asyncexitstack.py", line 20, in __call__
    raise e
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\fastapi\middleware\asyncexitstack.py", line 17, in __call__
    await self.app(scope, receive, send)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\routing.py", line 718, in __call__
    await route.handle(scope, receive, send)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\routing.py", line 276, in handle
    await self.app(scope, receive, send)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\starlette\routing.py", line 66, in app
    response = await func(request)
               ^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\fastapi\routing.py", line 274, in app
    raw_response = await run_endpoint_function(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\fastapi\routing.py", line 191, in run_endpoint_function
    return await dependant.call(**values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\api\v1\endpoints\places.py", line 15, in get_by_query
    places = await session.execute(select(PlacelistTable))
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\ext\asyncio\session.py", line 455, in execute
    result = await greenlet_spawn(
             ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\util\_concurrency_py3k.py", line 190, in greenlet_spawn
    result = context.throw(*sys.exc_info())
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 2308, in execute
    return self._execute_internal(
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\orm\session.py", line 2190, in _execute_internal
    result: Result[Any] = compile_state_cls.orm_execute_statement(
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\orm\context.py", line 293, in orm_execute_statement
    result = conn.execute(
             ^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1416, in execute
    return meth(
           ^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\sql\elements.py", line 516, in _execute_on_connection
    return connection._execute_clauseelement(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1639, in _execute_clauseelement
    ret = self._execute_context(
          ^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1848, in _execute_context
    return self._exec_single_context(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1988, in _exec_single_context
    self._handle_dbapi_exception(
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 2346, in _handle_dbapi_exception
    raise exc_info[1].with_traceback(exc_info[2])
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\base.py", line 1969, in _exec_single_context
    self.dialect.do_execute(
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\engine\default.py", line 922, in do_execute
    cursor.execute(statement, parameters)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\dialects\postgresql\asyncpg.py", line 591, in execute
    self._adapt_connection.await_(
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\util\_concurrency_py3k.py", line 125, in await_only
    return current.driver.switch(awaitable)  # type: ignore[no-any-return]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\util\_concurrency_py3k.py", line 185, in greenlet_spawn
    value = await result
            ^^^^^^^^^^^^
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\dialects\postgresql\asyncpg.py", line 527, in _prepare_and_execute
    await adapt_connection._start_transaction()
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\dialects\postgresql\asyncpg.py", line 861, in _start_transaction
    self._handle_exception(error)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\dialects\postgresql\asyncpg.py", line 810, in _handle_exception
    raise error
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\sqlalchemy\dialects\postgresql\asyncpg.py", line 859, in _start_transaction
    await self._transaction.start()
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\asyncpg\transaction.py", line 146, in start
    await self._connection.execute(query)
  File "C:\Users\dmm\testProject\venv\Lib\site-packages\asyncpg\connection.py", line 350, in execute
    result = await self._protocol.query(query, timeout)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "asyncpg\protocol\protocol.pyx", line 374, in query
  File "asyncpg\protocol\protocol.pyx", line 367, in asyncpg.protocol.protocol.BaseProtocol.query
  File "asyncpg\protocol\coreproto.pyx", line 1094, in asyncpg.protocol.protocol.CoreProtocol._simple_query
  File "asyncpg\protocol\protocol.pyx", line 966, in asyncpg.protocol.protocol.BaseProtocol._write
  File "C:\Users\dmm\AppData\Local\Programs\Python\Python312\Lib\asyncio\proactor_events.py", line 366, in write
    self._loop_writing(data=bytes(data))
  File "C:\Users\dmm\AppData\Local\Programs\Python\Python312\Lib\asyncio\proactor_events.py", line 402, in _loop_writing
    self._write_fut = self._loop._proactor.send(self._sock, data)
                      ^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'send'

我不明白她为什么会出现。我运行了调试器，一切都已创建。该async def get_all(session: AsyncSession = Depends(get_session)) -> list[Place]:会话不是 None 并且其状态是is_active。不知道可能是什么问题？

_session_maker: async_sessionmaker | None = None


async def get_session() -> AsyncSession:
    async with _session_maker() as session:
        yield session


async def init_db():
    global _session_maker
    engine = create_async_engine("postgresql+asyncpg://postgres:postgres@localhost/test")
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    _session_maker = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

@place_router.get("/")
async def get_all(session: AsyncSession = Depends(get_session)) -> list[Place]:
    places = await session.execute(select(PlaceTable))
    places = placelists.scalars().all()
    return places

async def main():
    await init_db()
    app = FastAPI(title=APP_NAME, version=API_VERSION)
    app.include_router(api_router)
    return app


if __name__ == "__main__":
    uvicorn.run(asyncio.run(main()), host="localhost", port=8000)

1 个回答

Voted

insolor · Answer 1 · 2023-11-13T16:39:28Z

在我看来，您运行应用程序的方式存在一些问题：

async def main():
    await init_db()
    app = FastAPI(title=APP_NAME, version=API_VERSION)
    app.include_router(api_router)
    return app


uvicorn.run(asyncio.run(main()), host="localhost", port=8000)

假设是：

在调用时，get_session该函数可能init_db没有时间执行，或者根本没有启动（或者在另一个进程中启动），因此，变量_session_maker包含None;
或者问题是由于asyncio.run事件循环开始然后结束，而 uvicorn 由于某种原因无法创建新的事件循环。

当在调试器下运行时，该函数可能有时间执行，或者在调试器下运行的一些其他功能有帮助。

我建议摆脱全局变量的使用，而是使其init_dbreturn session_maker，并向其添加异步缓存装饰器（如async-lru），以便它运行一次，然后只返回相同的值：

from async_lru import alru_cache  # pip install async-lru


async def get_session() -> AsyncSession:
    session_maker = await get_session_maker()
    async with session_maker() as session:
        yield session


@alru_cache()
async def get_session_maker():
    engine = create_async_engine("postgresql+asyncpg://postgres:postgres@localhost/test")
    async with engine.begin() as conn:
        await conn.run_sync(Base.metadata.create_all)
    return async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)

路由器不变，主文件变为“规范”形式：

app = FastAPI(title=APP_NAME, version=API_VERSION)
app.include_router(api_router)


if __name__ == "__main__":
    uvicorn.run(app, host="localhost", port=8000)

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1 个回答

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