FastAPI-SQLAlchemy 0.2.1

路线内部使用

注意，db.session提供的session对象基于Python3.7+ContextVar。这意味着 每个会话都链接到创建它的单个请求上下文。在

路线外使用

有时，能够在请求上下文之外访问数据库是很有用的，例如在后台运行的计划任务中：

importpytzfromapscheduler.schedulers.asyncioimportAsyncIOScheduler# other schedulers are availablefromfastapiimportFastAPIfromfastapi_sqlalchemyimportdbfromapp.modelsimportUser,UserCountapp=FastAPI()app.add_middleware(DBSessionMiddleware,db_url="sqlite://")@app.on_event('startup')asyncdefstartup_event():scheduler=AsyncIOScheduler(timezone=pytz.utc)scheduler.start()scheduler.add_job(count_users_task,"cron",hour=0)# runs every night at midnightdefcount_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:withdb():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 endedreturnusers