Classe « Session »

Méthode sqlalchemy.orm.Session.get

Signature de la méthode get

def get(self, entity, ident, options=None, populate_existing=False, with_for_update=None, identity_token=None) 

Description

get.__doc__

Return an instance based on the given primary key identifier,
        or ``None`` if not found.

        E.g.::

            my_user = session.get(User, 5)

            some_object = session.get(VersionedFoo, (5, 10))

            some_object = session.get(
                VersionedFoo,
                {"id": 5, "version_id": 10}
            )

        .. versionadded:: 1.4 Added :meth:`_orm.Session.get`, which is moved
           from the now deprecated :meth:`_orm.Query.get` method.

        :meth:`_orm.Session.get` is special in that it provides direct
        access to the identity map of the :class:`.Session`.
        If the given primary key identifier is present
        in the local identity map, the object is returned
        directly from this collection and no SQL is emitted,
        unless the object has been marked fully expired.
        If not present,
        a SELECT is performed in order to locate the object.

        :meth:`_orm.Session.get` also will perform a check if
        the object is present in the identity map and
        marked as expired - a SELECT
        is emitted to refresh the object as well as to
        ensure that the row is still present.
        If not, :class:`~sqlalchemy.orm.exc.ObjectDeletedError` is raised.

        :param entity: a mapped class or :class:`.Mapper` indicating the
         type of entity to be loaded.

        :param ident: A scalar, tuple, or dictionary representing the
         primary key.  For a composite (e.g. multiple column) primary key,
         a tuple or dictionary should be passed.

         For a single-column primary key, the scalar calling form is typically
         the most expedient.  If the primary key of a row is the value "5",
         the call looks like::

            my_object = session.get(SomeClass, 5)

         The tuple form contains primary key values typically in
         the order in which they correspond to the mapped
         :class:`_schema.Table`
         object's primary key columns, or if the
         :paramref:`_orm.Mapper.primary_key` configuration parameter were
         used, in
         the order used for that parameter. For example, if the primary key
         of a row is represented by the integer
         digits "5, 10" the call would look like::

             my_object = session.get(SomeClass, (5, 10))

         The dictionary form should include as keys the mapped attribute names
         corresponding to each element of the primary key.  If the mapped class
         has the attributes ``id``, ``version_id`` as the attributes which
         store the object's primary key value, the call would look like::

            my_object = session.get(SomeClass, {"id": 5, "version_id": 10})

        :param options: optional sequence of loader options which will be
         applied to the query, if one is emitted.

        :param populate_existing: causes the method to unconditionally emit
         a SQL query and refresh the object with the newly loaded data,
         regardless of whether or not the object is already present.

        :param with_for_update: optional boolean ``True`` indicating FOR UPDATE
          should be used, or may be a dictionary containing flags to
          indicate a more specific set of FOR UPDATE flags for the SELECT;
          flags should match the parameters of
          :meth:`_query.Query.with_for_update`.
          Supersedes the :paramref:`.Session.refresh.lockmode` parameter.

        :return: The object instance, or ``None``.