Pyramid SQLAlchemy session setup

example.py

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from zope.sqlalchemy import register


def get_sessionmaker(url, zope=True):
    """Configure a sessionmaker for use by requests.

    By default, sessions will attach themselves to the current transaction
    manager. Then can be turned off by setting ``zope=False``.
    """
    engine = create_engine(url)

    maker = sessionmaker()
    if zope:
        register(maker)

    maker.configure(bind=engine)
    return maker


def includeme(config):
    settings = config.get_settings()
    config.include('pyramid_tm')
    sessionmaker = get_sessionmaker(settings['database']['engine_url'])
    # Every request will have a db_session property. The first time
    # you use it, it creates a session, and then replaces the property
    # with that session.
    config.add_request_method(lambda request: sessionmaker(), 'db_session', reify=True)