SQLAlchemySessionManager (B)

gistfile1.py

# =========================================================================
# middleware.py
# =========================================================================
import sqlalchemy.orm.scoping as scoping


class SQLAlchemySessionManager(object):
    def __init__(self, session_factory, auto_commit=False):
        self._session_factory = session_factory
        self._scoped = isinstance(session_factory, scoping.ScopedSession)
        self._auto_commit = auto_commit

    def process_request(self, req, resp, params):
        req.context['session'] = self._session_factory()

    def process_response(self, req, resp):
        session = req.context['session']

        if self._auto_commit:
            session.commit()

        if self._scoped:
            session.remove()
        else:
            session.close()


# =========================================================================
# db.py
# =========================================================================
import sqlalchemy.orm as orm

Session = orm.scoped_session(orm.sessionmaker())


# =========================================================================
# app.py
# =========================================================================
import falcon
import sqlalchemy as sa

import db
import middleware


# TODO: Load engine options from a config file
engine = sa.create_engine('postgresql://scott:tiger@localhost/')
db.Session.configure(bind=engine)

session_manager = middleware.SQLAlchemySessionManager(db.Session)
api = falcon.API(middleware=[session_manager])

# Alternatively, you could use the global hooks mechanism, but that is 
# deprecated so will probably go away eventually (we need to sort out how
# to keep talons compatible with the latest falcon when that happens)
api_alt = falcon.API(before=[session_manager.process_request], 
                     after=[session_manager.process_response])


# =========================================================================
# somewhere_else.py
# =========================================================================

import db


class Foo(object):
    def do_something():
        # Get the scoped session object (from thread-local storage)
        session = db.Session()

        # <use the session>