Method instrument_class

lib/sqlalchemy/orm/events.py:890–920

r"""Receive a class when the mapper is first constructed, before instrumentation is applied to the mapped class. This event is the earliest phase of mapper construction. Most attributes of the mapper are not yet initialized. To receive an event within initial mappe

(self, mapper: Mapper[_O], class_: Type[_O])

        _MapperEventsHold._clear()

    def instrument_class(self, mapper: Mapper[_O], class_: Type[_O]) -> None:
        r"""Receive a class when the mapper is first constructed,
        before instrumentation is applied to the mapped class.

        This event is the earliest phase of mapper construction.
        Most attributes of the mapper are not yet initialized.   To
        receive an event within initial mapper construction where basic
        state is available such as the :attr:`_orm.Mapper.attrs` collection,
        the :meth:`_orm.MapperEvents.after_mapper_constructed` event may
        be a better choice.

        This listener can either be applied to the :class:`_orm.Mapper`
        class overall, or to any un-mapped class which serves as a base
        for classes that will be mapped (using the ``propagate=True`` flag)::

            Base = declarative_base()


            @event.listens_for(Base, "instrument_class", propagate=True)
            def on_new_class(mapper, cls_):
                "..."

        :param mapper: the :class:`_orm.Mapper` which is the target
         of this event.
        :param class\_: the mapped class.

        .. seealso::

            :meth:`_orm.MapperEvents.after_mapper_constructed`

        """

    def after_mapper_constructed(
        self, mapper: Mapper[_O], class_: Type[_O]