sqlalchemy.orm.attributes.AttributeEventToken

A token propagated throughout the course of a chain of attribute events. Serves as an indicator of the source of the event and also provides a means of controlling propagation across a chain of attribute operations. The :class:`.Event` object is sent as the ``initiator`` argument when dealing with events such as :meth:`.AttributeEvents.append`, :meth:`.AttributeEvents.set`, and :meth:`.AttributeEvents.remove`. The :class:`.Event` object is currently interpreted by the backref event handlers, and is used to control the propagation of operations across two mutually-dependent attributes. .. versionchanged:: 2.0 Changed the name from ``AttributeEvent`` to ``AttributeEventToken``. :attribute impl: The :class:`.AttributeImpl` which is the current event initiator. :attribute op: The symbol :attr:`.OP_APPEND`, :attr:`.OP_REMOVE`, :attr:`.OP_REPLACE`, or :attr:`.OP_BULK_REPLACE`, indicating the source operation.