Hi, because of legacy data which is not available in the database but some external files, I want to create a SQLAlchemy object which contains data read from the external files, but isn't written to the database if I execute session.flush() My code looks like this: try: return session.query(Phone).populate_existing().filter(Phone.mac == ident).one() except: return self.createMockPhoneFromLicenseFile(ident) def createMockPhoneFromLicenseFile(self, ident): # Some code to read necessary data from file deleted.... phone = Phone() phone.mac = foo phone.data = bar phone.state = "Read from legacy file" phone.purchaseOrderPosition = self.getLegacyOrder(ident) # SQLAlchemy magic doesn't seem to work here, probably because we don't insert the created # phone object into the database. So we set the id fields manually. phone.order_id = phone.purchaseOrderPosition.order_id phone.order_position_id = phone.purchaseOrderPosition.order_position_id return phone Everything works fine except that on a session.flush() executed later in the application SQLAlchemy tries to write the created Phone object to the database (which fortunatly doesn't succeed, because phone.state is longer than the data type allows), which breaks the function which issues the flush. Is there any way to prevent SQLAlchemy from trying to write such an object? Ciao, Steffen