Function column_property

lib/sqlalchemy/orm/_orm_constructors.py:459–629

r"""Provide a column-level property for use with a mapping. With Declarative mappings, :func:`_orm.column_property` is used to map read-only SQL expressions to a mapped class. When using Imperative mappings, :func:`_orm.column_property` also takes on the role of mapping table colum

(
    column: _ORMColumnExprArgument[_T],
    *additional_columns: _ORMColumnExprArgument[Any],
    group: Optional[str] = None,
    deferred: bool = False,
    raiseload: bool = False,
    comparator_factory: Optional[Type[PropComparator[_T]]] = None,
    init: Union[_NoArg, bool] = _NoArg.NO_ARG,
    repr: Union[_NoArg, bool] = _NoArg.NO_ARG,  # noqa: A002
    default: Optional[Any] = _NoArg.NO_ARG,
    default_factory: Union[_NoArg, Callable[[], _T]] = _NoArg.NO_ARG,
    compare: Union[_NoArg, bool] = _NoArg.NO_ARG,
    kw_only: Union[_NoArg, bool] = _NoArg.NO_ARG,
    hash: Union[_NoArg, bool, None] = _NoArg.NO_ARG,  # noqa: A002
    active_history: bool = False,
    expire_on_flush: bool = True,
    info: Optional[_InfoType] = None,
    doc: Optional[str] = None,
    dataclass_metadata: Union[_NoArg, Mapping[Any, Any], None] = _NoArg.NO_ARG,
)

    }
)
def column_property(
    column: _ORMColumnExprArgument[_T],
    *additional_columns: _ORMColumnExprArgument[Any],
    group: Optional[str] = None,
    deferred: bool = False,
    raiseload: bool = False,
    comparator_factory: Optional[Type[PropComparator[_T]]] = None,
    init: Union[_NoArg, bool] = _NoArg.NO_ARG,
    repr: Union[_NoArg, bool] = _NoArg.NO_ARG,  # noqa: A002
    default: Optional[Any] = _NoArg.NO_ARG,
    default_factory: Union[_NoArg, Callable[[], _T]] = _NoArg.NO_ARG,
    compare: Union[_NoArg, bool] = _NoArg.NO_ARG,
    kw_only: Union[_NoArg, bool] = _NoArg.NO_ARG,
    hash: Union[_NoArg, bool, None] = _NoArg.NO_ARG,  # noqa: A002
    active_history: bool = False,
    expire_on_flush: bool = True,
    info: Optional[_InfoType] = None,
    doc: Optional[str] = None,
    dataclass_metadata: Union[_NoArg, Mapping[Any, Any], None] = _NoArg.NO_ARG,
) -> MappedSQLExpression[_T]:
    r"""Provide a column-level property for use with a mapping.

    With Declarative mappings, :func:`_orm.column_property` is used to
    map read-only SQL expressions to a mapped class.

    When using Imperative mappings, :func:`_orm.column_property` also
    takes on the role of mapping table columns with additional features.
    When using fully Declarative mappings, the :func:`_orm.mapped_column`
    construct should be used for this purpose.

    With Declarative Dataclass mappings, :func:`_orm.column_property`
    is considered to be **read only**, and will not be included in the
    Dataclass ``__init__()`` constructor.

    The :func:`_orm.column_property` function returns an instance of
    :class:`.ColumnProperty`.

    .. seealso::

        :ref:`mapper_column_property_sql_expressions` - general use of
        :func:`_orm.column_property` to map SQL expressions

        :ref:`orm_imperative_table_column_options` - usage of
        :func:`_orm.column_property` with Imperative Table mappings to apply
        additional options to a plain :class:`_schema.Column` object

    :param \*cols:
        list of Column objects to be mapped.

    :param active_history=False:

        Used only for Imperative Table mappings, or legacy-style Declarative
        mappings (i.e. which have not been upgraded to
        :func:`_orm.mapped_column`), for column-based attributes that are
        expected to be writeable; use :func:`_orm.mapped_column` with
        :paramref:`_orm.mapped_column.active_history` for Declarative mappings.
        See that parameter for functional details.