Class ZeroOrOne

src/pptx/oxml/xmlchemy.py:558–597

Defines an optional child element for MetaOxmlElement.

class ZeroOrOne(_BaseChildElement):
    """Defines an optional child element for MetaOxmlElement."""

    def populate_class_members(self, element_cls: Type[BaseOxmlElement], prop_name: str):
        """Add the appropriate methods to `element_cls`."""
        super(ZeroOrOne, self).populate_class_members(element_cls, prop_name)
        self._add_getter()
        self._add_creator()
        self._add_inserter()
        self._add_adder()
        self._add_get_or_adder()
        self._add_remover()

    def _add_get_or_adder(self):
        """Add a `.get_or_add_x()` method to the element class for this child element."""

        def get_or_add_child(obj: BaseOxmlElement) -> BaseOxmlElement:
            child = getattr(obj, self._prop_name)
            if child is None:
                add_method = getattr(obj, self._add_method_name)
                child = add_method()
            return child

        get_or_add_child.__doc__ = (
            "Return the ``<%s>`` child element, newly added if not present."
        ) % self._nsptagname
        self._add_to_class(self._get_or_add_method_name, get_or_add_child)

    def _add_remover(self):
        """Add a `._remove_x()` method to the element class for this child element."""

        def _remove_child(obj: BaseOxmlElement) -> None:
            obj.remove_all(self._nsptagname)

        _remove_child.__doc__ = f"Remove all `{self._nsptagname}` child elements."
        self._add_to_class(self._remove_method_name, _remove_child)

    @lazyproperty
    def _get_or_add_method_name(self):
        return "get_or_add_%s" % self._prop_name


class ZeroOrOneChoice(_BaseChildElement):