Method __get__

lib/sqlalchemy/orm/decl_api.py:272–309

(self, instance: Optional[object], owner: Any)

        return util.get_annotations(self.fget).get("return")

    def __get__(self, instance: Optional[object], owner: Any) -> Any:
        # the declared_attr needs to make use of a cache that exists
        # for the span of the declarative scan_attributes() phase.
        # to achieve this we look at the class manager that's configured.

        # note this method should not be called outside of the declarative
        # setup phase

        cls = owner
        manager = attributes.opt_manager_of_class(cls)
        if manager is None:
            if not re.match(r"^__.+__$", self.fget.__name__):
                # if there is no manager at all, then this class hasn't been
                # run through declarative or mapper() at all, emit a warning.
                util.warn(
                    "Unmanaged access of declarative attribute %s from "
                    "non-mapped class %s" % (self.fget.__name__, cls.__name__)
                )
            return self.fget(cls)
        elif manager.is_mapped:
            # the class is mapped, which means we're outside of the declarative
            # scan setup, just run the function.
            return self.fget(cls)

        # here, we are inside of the declarative scan.  use the registry
        # that is tracking the values of these attributes.
        declarative_scan = manager.declarative_scan()

        # assert that we are in fact in the declarative scan
        assert declarative_scan is not None

        reg = declarative_scan.declared_attr_reg

        if self in reg:
            return reg[self]
        else:
            reg[self] = obj = self.fget(cls)
            return obj


class _declared_directive(_declared_attr_common, Generic[_T]):