'async_generator is not a callable object' FastAPI dependency issue app

Question

I am trying to create a FastAPI and async sqlalchemy.

The get_db dependency causes a weird TypeError: <async_generator object get_db at 0x7ff6d9d9aa60> is not a callable object issue.

Here's my code:

db.py

from typing import Generator
from .db.session import SessionLocal

async def get_db() -> Generator:
    try:
        db = SessionLocal()
        yield db
    finally:
        await db.close()

session.py

from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession
from .core.config import settings

engine = create_async_engine(
    settings.SQLALCHEMY_DATABASE_URI,
    pool_pre_ping=True
)
SessionLocal = AsyncSession(
    autocommit=False,
    autoflush=False,
    bind=engine
)

I followed almost of the instructions posted here: https://6060ff4ffd0e7c1b62baa6c7--fastapi.netlify.app/advanced/sql-databases-sqlalchemy/#more-info

Answer 1

I have figured this out, basically when you call the generator get_db() as a dependency for a FastAPI endpoint, you basically just call it as get_db without the parenthesis.

For example:

from typing import List, Any

from fastapi import APIRouter, HTTPException, Depends, status
from sqlalchemy.ext.asyncio import AsyncSession

from . import models, crud, schemas
from .deps.db import get_db

router = APIRouter()


@router.post('/',
             response_model=schemas.StaffAccount,
             status_code=status.HTTP_201_CREATED)
async def create_staff_account(
        db: AsyncSession = Depends(get_db),
        staff_acct: schemas.StaffAccountCreate = Depends(schemas.StaffAccountCreate)
) -> Any:
    q = await crud.staff.create(db=db, obj_in=staff_acct)
    if not q:
        raise HTTPException(status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
                            detail='An error occurred while processing your request')
    return q

This is such a minor detail, that can get in the way of some beginners (like me). So please look more closely at your code.