👀 Views: 98 💬 Answers: 1 📅 Created: 2025-06-22

fastapi asyncio sqlalchemy Python

I'm working through a tutorial and I just started working with I tried several approaches but none seem to work... I'm running into an issue with an asynchronous function in my FastAPI application where it seems that the data being processed isn't consistent. I have an endpoint that fetches data from a database and then processes it before returning the result. However, when I hit the endpoint multiple times, sometimes the data returned is stale or not what I expect, indicating that the asynchronous handling might not be working correctly. Here's a simplified version of my code: ```python from fastapi import FastAPI from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker, declarative_base from sqlalchemy.future import select DATABASE_URL = "postgresql+asyncpg://user:password@localhost/db_name" engine = create_async_engine(DATABASE_URL, echo=True) Base = declarative_base() async_session = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession) app = FastAPI() class Item(Base): __tablename__ = 'items' id = Column(Integer, primary_key=True) name = Column(String) @app.get("/items/{item_id}") async def read_item(item_id: int): async with async_session() as session: stmt = select(Item).where(Item.id == item_id) result = await session.execute(stmt) item = result.scalar_one_or_none() return item ``` When I call this endpoint, I sometimes receive the expected item, but often I get an item that hasn't been updated in the database. I suspect it's related to how I'm managing the session or the async context. I also tried adding logging to see if the session is being created and closed properly, and it seems to be, but I still run into these inconsistency issues. I've tried using `await` on the `session.execute` call, and I've checked that the database has the latest data. I'm using FastAPI version 0.68.0 and SQLAlchemy version 1.4.25. Is there something I might be missing in terms of the async handling or session management that could lead to this problem? Thanks in advance! What's the best practice here? I'm using Python stable in this project. What's the correct way to implement this?