👀 Views: 67 💬 Answers: 1 📅 Created: 2025-06-03

fastapi sqlalchemy asyncio Python

I'm experimenting with I'm maintaining legacy code that I tried several approaches but none seem to work. I've been researching this but I've been banging my head against this for hours... I'm working on a FastAPI application and running into a question where my async function that queries the database is returning `None` instead of the expected data. I'm using SQLAlchemy with an async database session. Here's what my code looks like: ```python from fastapi import FastAPI, Depends from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker from sqlalchemy import select DATABASE_URL = 'postgresql+asyncpg://user:password@localhost/dbname' engine = create_async_engine(DATABASE_URL) Base = declarative_base() AsyncSessionLocal = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False) app = FastAPI() class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True, index=True) name = Column(String, index=True) async def get_db(): async with AsyncSessionLocal() as session: yield session @app.get('/users/{user_id}') async def read_user(user_id: int, db: AsyncSession = Depends(get_db)): stmt = select(User).where(User.id == user_id) result = await db.execute(stmt) user = result.scalars().first() return user ``` When I access the endpoint `/users/1`, it returns `null` even though I have a user with that ID in the database. I've checked the database connection, and it seems fine. I also tried adding print statements to debug and verified that the query is being executed, but `user` remains `None`. I've also confirmed that the table and column names match correctly. I’m using FastAPI version 0.78.0 and SQLAlchemy 1.4.27. Any help or suggestions on what I might be missing would be greatly appreciated! For context: I'm using Python on Windows. Any help would be greatly appreciated! I recently upgraded to Python latest. I'm open to any suggestions. Any advice would be much appreciated. Am I missing something obvious? I'm using Python latest in this project. Is this even possible? My team is using Python for this microservice. Any pointers in the right direction?