Adds simple SQLAlchemy support to FastAPI
Install and update using pip:
$ pip install fastapi-sqlalchemy
Usage inside of a route
from fastapi import FastAPI from fastapi_sqlalchemy import DBSessionMiddleware # middleware helper from fastapi_sqlalchemy import db # an object to provide global access to a database session from app.models import User app = FastAPI() app.add_middleware(DBSessionMiddleware, db_url="sqlite://") # once the middleware is applied, any route can then access the database session # from the global ``db`` @app.get("/users") def get_users(): users = db.session.query(User).all() return users
Note that the session object provided by db.session is based on the Python3.7+ ContextVar. This means that each session is linked to the individual request context in which it was created.
Usage outside of a route
Sometimes it is useful to be able to access the database outside the context of a request, such as in scheduled tasks which run in the background:
import pytz from apscheduler.schedulers.asyncio import AsyncIOScheduler # other schedulers are available from fastapi import FastAPI from fastapi_sqlalchemy import db from app.models import User, UserCount app = FastAPI() app.add_middleware(DBSessionMiddleware, db_url="sqlite://") @app.on_event('startup') async def startup_event(): scheduler = AsyncIOScheduler(timezone=pytz.utc) scheduler.start() scheduler.add_job(count_users_task, "cron", hour=0) # runs every night at midnight def count_users_task(): """Count the number of users in the database and save it into the user_counts table.""" # we are outside of a request context, therefore we cannot rely on ``DBSessionMiddleware`` # to create a database session for us. Instead, we can use the same ``db`` object and # use it as a context manager, like so: with db(): user_count = db.session.query(User).count() db.session.add(UserCount(user_count)) db.session.commit() # no longer able to access a database session once the db() context manager has ended return users
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