CriteriaResultOutputParser Class — langchain Architecture

Source Code

libs/langchain/langchain_classic/evaluation/criteria/eval_chain.py lines 66–110

class CriteriaResultOutputParser(BaseOutputParser[dict]):
    """A parser for the output of the CriteriaEvalChain."""

    @property
    def _type(self) -> str:
        return "criteria_result"

    def parse(self, text: str) -> dict[str, Any]:
        """Parse the output text.

        Args:
            text: The output text to parse.

        Returns:
            The parsed output.
        """
        verdict = None
        score = None
        match_last = re.search(r"\s*(Y|N)\s*$", text, re.IGNORECASE)
        match_first = re.search(r"^\s*(Y|N)\s*", text, re.IGNORECASE)
        match_end = re.search(r"\b(Y|N)\b\s*$", text, re.IGNORECASE)

        if match_last:
            verdict = match_last.group(1).strip()
            text = text[: match_last.start()].strip()
        elif match_first:
            verdict = match_first.group(1).strip()
            text = text[match_first.end() :].strip()
        elif match_end:
            verdict = match_end.group(1).strip()
            text = text[: match_end.start()].strip()
        else:
            splits = text.strip().rsplit("\n", maxsplit=1)
            verdict = splits[-1]

        if verdict:
            score = (
                1 if verdict.upper() == "Y" else (0 if verdict.upper() == "N" else None)
            )

        return {
            "reasoning": text.strip(),
            "value": verdict,
            "score": score,
        }