Class OneAndOnlyOne

src/pptx/oxml/xmlchemy.py:474–500

Defines a required child element for MetaOxmlElement.

class OneAndOnlyOne(_BaseChildElement):
    """Defines a required child element for MetaOxmlElement."""

    def __init__(self, nsptagname: str):
        super(OneAndOnlyOne, self).__init__(nsptagname, ())

    def populate_class_members(self, element_cls: Type[BaseOxmlElement], prop_name: str):
        """
        Add the appropriate methods to *element_cls*.
        """
        super(OneAndOnlyOne, self).populate_class_members(element_cls, prop_name)
        self._add_getter()

    @property
    def _getter(self) -> Callable[[BaseOxmlElement], BaseOxmlElement]:
        """Callable suitable for the "get" side of the property descriptor."""

        def get_child_element(obj: BaseOxmlElement) -> BaseOxmlElement:
            child = obj.find(qn(self._nsptagname))
            if child is None:
                raise InvalidXmlError(
                    "required ``<%s>`` child element not present" % self._nsptagname
                )
            return child

        get_child_element.__doc__ = "Required ``<%s>`` child element." % self._nsptagname
        return get_child_element


class OneOrMore(_BaseChildElement):