try:
    webapp2.RequestHandler.dispatch(self)
finally:
    self.session_store.save_sessions(self.response)

@webapp2.cached_property
def session(self):
    return self.session_store.get_session()
self.session['foo'] = 'bar'
foo = self.session.get('foo')
Google App Engine — Получение сеансов, работающих с Python 2.7