RouterOutputParser Class — langchain Architecture

Source Code

libs/langchain/langchain_classic/chains/router/llm_router.py lines 167–196

class RouterOutputParser(BaseOutputParser[dict[str, str]]):
    """Parser for output of router chain in the multi-prompt chain."""

    default_destination: str = "DEFAULT"
    next_inputs_type: type = str
    next_inputs_inner_key: str = "input"

    @override
    def parse(self, text: str) -> dict[str, Any]:
        try:
            expected_keys = ["destination", "next_inputs"]
            parsed = parse_and_check_json_markdown(text, expected_keys)
            if not isinstance(parsed["destination"], str):
                msg = "Expected 'destination' to be a string."
                raise TypeError(msg)
            if not isinstance(parsed["next_inputs"], self.next_inputs_type):
                msg = f"Expected 'next_inputs' to be {self.next_inputs_type}."
                raise TypeError(msg)
            parsed["next_inputs"] = {self.next_inputs_inner_key: parsed["next_inputs"]}
            if (
                parsed["destination"].strip().lower()
                == self.default_destination.lower()
            ):
                parsed["destination"] = None
            else:
                parsed["destination"] = parsed["destination"].strip()
        except Exception as e:
            msg = f"Parsing text\n{text}\n raised following error:\n{e}"
            raise OutputParserException(msg) from e
        return parsed