Method one

lib/sqlalchemy/orm/query.py:2794–2815

Return exactly one result or raise an exception. Raises :class:`_exc.NoResultFound` if the query selects no rows. Raises :class:`_exc.MultipleResultsFound` if multiple object identities are returned, or if multiple rows are returned for a query that returns only scal

(self)

        return self._iter().one_or_none()  # type: ignore

    def one(self) -> _T:
        """Return exactly one result or raise an exception.

        Raises :class:`_exc.NoResultFound` if the query selects no rows.
        Raises :class:`_exc.MultipleResultsFound` if multiple object identities
        are returned, or if multiple rows are returned for a query that returns
        only scalar values as opposed to full identity-mapped entities.

        Calling :meth:`.one` results in an execution of the underlying query.

        .. seealso::

            :meth:`_query.Query.first`

            :meth:`_query.Query.one_or_none`

            :meth:`_engine.Result.one` - v2 comparable method.

            :meth:`_engine.Result.scalar_one` - v2 comparable method.

        """
        return self._iter().one()  # type: ignore

    def scalar(self) -> Any:
        """Return the first element of the first result or None