Class ScalarSelect

lib/sqlalchemy/sql/selectable.py:6747–6891

Represent a scalar subquery. A :class:`_sql.ScalarSelect` is created by invoking the :meth:`_sql.SelectBase.scalar_subquery` method. The object then participates in other SQL expressions as a SQL column expression within the :class:`_sql.ColumnElement` hierarchy. .. seealso:

class ScalarSelect(
    roles.InElementRole, Generative, GroupedElement, ColumnElement[_T]
):
    """Represent a scalar subquery.


    A :class:`_sql.ScalarSelect` is created by invoking the
    :meth:`_sql.SelectBase.scalar_subquery` method.   The object
    then participates in other SQL expressions as a SQL column expression
    within the :class:`_sql.ColumnElement` hierarchy.

    .. seealso::

        :meth:`_sql.SelectBase.scalar_subquery`

        :ref:`tutorial_scalar_subquery` - in the 2.0 tutorial

    """

    _traverse_internals: _TraverseInternalsType = [
        ("element", InternalTraversal.dp_clauseelement),
        ("type", InternalTraversal.dp_type),
    ]

    _from_objects: List[FromClause] = []
    _is_from_container = True
    if not TYPE_CHECKING:
        _is_implicitly_boolean = False
    inherit_cache = True

    element: SelectBase

    def __init__(self, element: SelectBase) -> None:
        self.element = element
        self.type = element._scalar_type()
        self._propagate_attrs = element._propagate_attrs

    def __getattr__(self, attr: str) -> Any:
        return getattr(self.element, attr)

    def __getstate__(self) -> Dict[str, Any]:
        return {"element": self.element, "type": self.type}

    def __setstate__(self, state: Dict[str, Any]) -> None:
        self.element = state["element"]
        self.type = state["type"]

    @property
    def columns(self) -> NoReturn:
        raise exc.InvalidRequestError(
            "Scalar Select expression has no "
            "columns; use this object directly "
            "within a column-level expression."
        )

    c = columns

    @_generative