【AI】async如何使用

1. async def

1.1 async def + yield

# Pattern 1： yield + use async for
async def get_sers():
	yield user1

async def my_function():
	async for user in get_users():
		process(ser)

# wrong - can't await an AsyncGenerator
result = await get_sers() # TypeError

1.2 async def + return

async def get_user():
	return single_ser

# correct consumption
async def my_function():
	user = await get_ser()

# Wrong - can't iterate a Corotine
async for u in get_user():	# TypeError

2. async with

async def get_session() -> AsyncGenerator[AsyncSession, None]:  # 3 ✅
    # db_local_session = async_sessionmaker(...)
    async with Database.db_local_session() as session:  # 1 ✅
        try:
            yield session  # 4a ✅ `yield` relates to `async def`, the caller needs to use `async for`
            await session.commit()  # 2 ✅
        except Exception:
            await session.rollback()
            raise


# ✅ Correct usage - async context manager
@asynccontextmanager
async def get_db_session() -> AsyncIterator[AsyncSession]:
    async for session in Database.get_session():  # 4b ✅
        yield session