engine = create_engine("...")
Session = sessionmaker(bind=engine)
# new session. no connections are in use.
session = Session()
try:
# first query. a Connection is acquired
# from the Engine, and a Transaction
# started.
item1 = session.query(Item).get(1)
# second query. the same Connection/Transaction
# are used.
item2 = session.query(Item).get(2)
# pending changes are created.
item1.foo = ’bar’
item2.bar = ’foo’
# commit. The pending changes above
# are flushed via flush(), the Transaction
# is committed, the Connection object closed
# and discarded, the underlying DBAPI connection
# returned to the connection pool.
session.commit()
except:
# on rollback, the same closure of state
# as that of commit proceeds.
session.rollback()
raise