Class sessionmaker

lib/sqlalchemy/orm/session.py:5098–5327

A configurable :class:`.Session` factory. The :class:`.sessionmaker` factory generates new :class:`.Session` objects when called, creating them given the configurational arguments established here. e.g.:: from sqlalchemy import create_engine from sqlalchemy.orm imp

class sessionmaker(_SessionClassMethods, Generic[_S]):
    """A configurable :class:`.Session` factory.

    The :class:`.sessionmaker` factory generates new
    :class:`.Session` objects when called, creating them given
    the configurational arguments established here.

    e.g.::

        from sqlalchemy import create_engine
        from sqlalchemy.orm import sessionmaker

        # an Engine, which the Session will use for connection
        # resources
        engine = create_engine("postgresql+psycopg2://scott:tiger@localhost/")

        Session = sessionmaker(engine)

        with Session() as session:
            session.add(some_object)
            session.add(some_other_object)
            session.commit()

    Context manager use is optional; otherwise, the returned
    :class:`_orm.Session` object may be closed explicitly via the
    :meth:`_orm.Session.close` method.   Using a
    ``try:/finally:`` block is optional, however will ensure that the close
    takes place even if there are database errors::

        session = Session()
        try:
            session.add(some_object)
            session.add(some_other_object)
            session.commit()
        finally:
            session.close()

    :class:`.sessionmaker` acts as a factory for :class:`_orm.Session`
    objects in the same way as an :class:`_engine.Engine` acts as a factory
    for :class:`_engine.Connection` objects.  In this way it also includes
    a :meth:`_orm.sessionmaker.begin` method, that provides a context
    manager which both begins and commits a transaction, as well as closes
    out the :class:`_orm.Session` when complete, rolling back the transaction
    if any errors occur::

        Session = sessionmaker(engine)

        with Session.begin() as session:
            session.add(some_object)
            session.add(some_other_object)
        # commits transaction, closes session

    .. versionadded:: 1.4

    When calling upon :class:`_orm.sessionmaker` to construct a
    :class:`_orm.Session`, keyword arguments may also be passed to the
    method; these arguments will override that of the globally configured
    parameters.  Below we use a :class:`_orm.sessionmaker` bound to a certain