scoped_session(sessionmaker()) or plain sessionmaker() in sqlalchemy?

Question

I am using SQlAlchemy in my web project. What should I use - scoped_session(sessionmaker()) or plain sessionmaker() - and why? Or should I use something else?

## model.py from sqlalchemy import * from sqlalchemy.orm import *  engine = create_engine('mysql://dbUser:dbPassword@dbServer:dbPort/dbName', pool_recycle=3600, echo=False) metadata = MetaData(engine) Session = scoped_session(sessionmaker()) Session.configure(bind=engine) user = Table('user', metadata, autoload=True)  class User(object): pass  usermapper = mapper(User, user)  ## some other python file called abc.py from models import *  def getalluser():    session = Session()      session.query(User).all()    session.flush()    session.close()  ## onemore file defg.py from models import *  def updateuser():    session = Session()      session.query(User).filter(User.user_id == '4').update({User.user_lname: 'villkoo'})    session.commit()    session.flush()    session.close() 

I create a session = Session() object for each request and I close it. Am I doing the right thing or is there a better way to do it?

Answer 1

Reading the documentation is recommended:

the scoped_session() function is provided which produces a thread-managed registry of Session objects. It is commonly used in web applications so that a single global variable can be used to safely represent transactional sessions with sets of objects, localized to a single thread.

In short, use scoped_session() for thread safety.