Class _Relationship

src/pptx/opc/package.py:680–762

Value object describing link from a part or package to another part.

class _Relationship:
    """Value object describing link from a part or package to another part."""

    def __init__(self, base_uri: str, rId: str, reltype: str, target_mode: str, target: Part | str):
        self._base_uri = base_uri
        self._rId = rId
        self._reltype = reltype
        self._target_mode = target_mode
        self._target = target

    @classmethod
    def from_xml(
        cls, base_uri: str, rel: CT_Relationship, parts: dict[PackURI, Part]
    ) -> _Relationship:
        """Return |_Relationship| object based on CT_Relationship element `rel`."""
        target = (
            rel.target_ref
            if rel.targetMode == RTM.EXTERNAL
            else parts[PackURI.from_rel_ref(base_uri, rel.target_ref)]
        )
        return cls(base_uri, rel.rId, rel.reltype, rel.targetMode, target)

    @lazyproperty
    def is_external(self) -> bool:
        """True if target_mode is `RTM.EXTERNAL`.

        An external relationship is a link to a resource outside the package, such as a
        web-resource (URL).
        """
        return self._target_mode == RTM.EXTERNAL

    @lazyproperty
    def reltype(self) -> str:
        """Member of RELATIONSHIP_TYPE describing relationship of target to source."""
        return self._reltype

    @lazyproperty
    def rId(self) -> str:
        """str relationship-id, like 'rId9'.

        Corresponds to the `Id` attribute on the `CT_Relationship` element and uniquely identifies
        this relationship within its peers for the source-part or package.
        """
        return self._rId

    @lazyproperty
    def target_part(self) -> Part:
        """|Part| or subtype referred to by this relationship."""
        if self.is_external:
            raise ValueError(
                "`.target_part` property on _Relationship is undefined when "
                "target-mode is external"
            )
        assert isinstance(self._target, Part)
        return self._target

    @lazyproperty
    def target_partname(self) -> PackURI: