Class Boolean

lib/sqlalchemy/sql/sqltypes.py:2092–2228

A bool datatype. :class:`.Boolean` typically uses BOOLEAN or SMALLINT on the DDL side, and on the Python side deals in ``True`` or ``False``. The :class:`.Boolean` datatype currently has two levels of assertion that the values persisted are simple true/false values. For all ba

class Boolean(SchemaType, Emulated, TypeEngine[bool]):
    """A bool datatype.

    :class:`.Boolean` typically uses BOOLEAN or SMALLINT on the DDL side,
    and on the Python side deals in ``True`` or ``False``.

    The :class:`.Boolean` datatype currently has two levels of assertion
    that the values persisted are simple true/false values.  For all
    backends, only the Python values ``None``, ``True``, ``False``, ``1``
    or ``0`` are accepted as parameter values.   For those backends that
    don't support a "native boolean" datatype, an option exists to
    also create a CHECK constraint on the target column

    """

    __visit_name__ = "boolean"
    native = True

    operator_classes = OperatorClass.BOOLEAN

    def __init__(
        self,
        create_constraint: bool = False,
        name: Optional[str] = None,
        _create_events: bool = True,
        _adapted_from: Optional[SchemaType] = None,
    ):
        """Construct a Boolean.

        :param create_constraint: defaults to False.  If the boolean
          is generated as an int/smallint, also create a CHECK constraint
          on the table that ensures 1 or 0 as a value.

          .. note:: it is strongly recommended that the CHECK constraint
             have an explicit name in order to support schema-management
             concerns.  This can be established either by setting the
             :paramref:`.Boolean.name` parameter or by setting up an
             appropriate naming convention; see
             :ref:`constraint_naming_conventions` for background.

          .. versionchanged:: 1.4 - this flag now defaults to False, meaning
             no CHECK constraint is generated for a non-native enumerated
             type.

        :param name: if a CHECK constraint is generated, specify
          the name of the constraint.

        """
        self.create_constraint = create_constraint
        self.name = name
        self._create_events = _create_events
        if _adapted_from:
            self.dispatch = self.dispatch._join(_adapted_from.dispatch)

    def copy(self, **kw):
        # override SchemaType.copy() to not include to_metadata logic
        return self.adapt(
            cast("Type[TypeEngine[Any]]", self.__class__),