Method before_insert

lib/sqlalchemy/orm/events.py:1164–1216

Receive an object instance before an INSERT statement is emitted corresponding to that instance. .. note:: this event **only** applies to the :ref:`session flush operation <session_flushing>` and does **not** apply to the ORM DML operations described at

(
        self, mapper: Mapper[_O], connection: Connection, target: _O
    )

        """

    def before_insert(
        self, mapper: Mapper[_O], connection: Connection, target: _O
    ) -> None:
        """Receive an object instance before an INSERT statement
        is emitted corresponding to that instance.

        .. note:: this event **only** applies to the
           :ref:`session flush operation <session_flushing>`
           and does **not** apply to the ORM DML operations described at
           :ref:`orm_expression_update_delete`.  To intercept ORM
           DML events, use :meth:`_orm.SessionEvents.do_orm_execute`.

        This event is used to modify local, non-object related
        attributes on the instance before an INSERT occurs, as well
        as to emit additional SQL statements on the given
        connection.

        The event is often called for a batch of objects of the
        same class before their INSERT statements are emitted at
        once in a later step. In the extremely rare case that
        this is not desirable, the :class:`_orm.Mapper` object can be
        configured with ``batch=False``, which will cause
        batches of instances to be broken up into individual
        (and more poorly performing) event->persist->event
        steps.

        .. warning::

            Mapper-level flush events only allow **very limited operations**,
            on attributes local to the row being operated upon only,
            as well as allowing any SQL to be emitted on the given
            :class:`_engine.Connection`.  **Please read fully** the notes
            at :ref:`session_persistence_mapper` for guidelines on using
            these methods; generally, the :meth:`.SessionEvents.before_flush`
            method should be preferred for general on-flush changes.

        :param mapper: the :class:`_orm.Mapper` which is the target
         of this event.
        :param connection: the :class:`_engine.Connection` being used to
         emit INSERT statements for this instance.  This
         provides a handle into the current transaction on the
         target database specific to this instance.
        :param target: the mapped instance being persisted.  If
         the event is configured with ``raw=True``, this will
         instead be the :class:`.InstanceState` state-management
         object associated with the instance.
        :return: No return value is supported by this event.

        .. seealso::

            :ref:`session_persistence_events`

        """

    def after_insert(
        self, mapper: Mapper[_O], connection: Connection, target: _O