Class Cast

lib/sqlalchemy/sql/elements.py:3397–3454

Represent a ``CAST`` expression. :class:`.Cast` is produced using the :func:`.cast` factory function, as in:: from sqlalchemy import cast, Numeric stmt = select(cast(product_table.c.unit_price, Numeric(10, 4))) Details on :class:`.Cast` usage is at :func:`.cast`.

class Cast(WrapsColumnExpression[_T]):
    """Represent a ``CAST`` expression.

    :class:`.Cast` is produced using the :func:`.cast` factory function,
    as in::

        from sqlalchemy import cast, Numeric

        stmt = select(cast(product_table.c.unit_price, Numeric(10, 4)))

    Details on :class:`.Cast` usage is at :func:`.cast`.

    .. seealso::

        :ref:`tutorial_casts`

        :func:`.cast`

        :func:`.try_cast`

        :func:`.type_coerce` - an alternative to CAST that coerces the type
        on the Python side only, which is often sufficient to generate the
        correct SQL and data coercion.

    """

    __visit_name__ = "cast"

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

    clause: ColumnElement[Any]
    type: TypeEngine[_T]
    typeclause: TypeClause

    def __init__(
        self,
        expression: _ColumnExpressionArgument[Any],
        type_: _TypeEngineArgument[_T],
    ):
        self.type = type_api.to_instance(type_)
        self.clause = coercions.expect(
            roles.ExpressionElementRole,
            expression,
            type_=self.type,
            apply_propagate_attrs=self,
        )
        self.typeclause = TypeClause(self.type)

    @util.ro_non_memoized_property
    def _from_objects(self) -> List[FromClause]:
        return self.clause._from_objects

    @property
    def wrapped_column_expression(self):
        return self.clause