_parse_json_string() — langchain Function Reference

Source Code

libs/partners/ollama/langchain_ollama/chat_models.py lines 118–167

def _parse_json_string(
    json_string: str,
    *,
    raw_tool_call: dict[str, Any],
    skip: bool,
) -> Any:
    """Attempt to parse a JSON string for tool calling.

    It first tries to use the standard `json.loads`. If that fails, it falls
    back to `ast.literal_eval` to safely parse Python literals, which is more
    robust against models using single quotes or containing apostrophes.

    Args:
        json_string: JSON string to parse.
        raw_tool_call: Raw tool call to include in error message.
        skip: Whether to ignore parsing errors and return the value anyways.

    Returns:
        The parsed JSON string or Python literal.

    Raises:
        OutputParserException: If the string is invalid and `skip=False`.
    """
    try:
        return json.loads(json_string)
    except json.JSONDecodeError:
        try:
            # Use ast.literal_eval to safely parse Python-style dicts
            # (e.g. with single quotes)
            return ast.literal_eval(json_string)
        except (SyntaxError, ValueError) as e:
            # If both fail, and we're not skipping, raise an informative error.
            if skip:
                return json_string
            msg = (
                f"Function {raw_tool_call['function']['name']} arguments:\n\n"
                f"{raw_tool_call['function']['arguments']}"
                "\n\nare not valid JSON or a Python literal. "
                f"Received error: {e}"
            )
            raise OutputParserException(msg) from e
    except TypeError as e:
        if skip:
            return json_string
        msg = (
            f"Function {raw_tool_call['function']['name']} arguments:\n\n"
            f"{raw_tool_call['function']['arguments']}\n\nare not a string or a "
            f"dictionary. Received TypeError {e}"
        )
        raise OutputParserException(msg) from e