There should be a __delete__ method that ORM classes can define

[Former user]

Since an object can continue to exist in Python memory indefinitely after session.delete(...) has been called to remove it from the database, it would be fun if objects could define __delete__() and if SQLAlchemy would call that routine when an object was removed from the database. This could be the beginning of trigger-like functionality in SQLAlchemy.

A difficulty is that an object can be deleted from the database with session.delete(...), and then be added back with session.save(...) later. I can't imagine a use case for that, but it looks entirely possible. Therefore there might need to be a symmetrical __insert__() method that can tell the object it's live and stored in a database again so that it can do the reverse of whatever cleanup the object wanted done when the user removed it.

[Mike Bayer]

this is supplied by MapperExtension.after_delete() and is straightforward to hook up to an on-class __delete__() method.

There's been discussion about providing a prefab sqla extension module which supplies all the MapperExtension persistence methods on a class (or maybe as decorators) but end-user versions of this are trivial.