parse() — langchain Function Reference

Architecture documentation for the parse() function in react_single_input.py from the langchain codebase.

Function python AgentOrchestration ClassicChains

Entity Profile

AgentOrchestration→ ClassicChains→ parse() — langchain Function Reference

Dependency Diagram

graph TD
  7d02b89a_0f19_a4f4_59fd_ff7b5791e7cf["parse()"]
  44a4a52d_37e0_f939_5bc2_6364be670573["ReActSingleInputOutputParser"]
  7d02b89a_0f19_a4f4_59fd_ff7b5791e7cf -->|defined in| 44a4a52d_37e0_f939_5bc2_6364be670573
  style 7d02b89a_0f19_a4f4_59fd_ff7b5791e7cf fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/langchain/langchain_classic/agents/output_parsers/react_single_input.py lines 53–97

    def parse(self, text: str) -> AgentAction | AgentFinish:
        includes_answer = FINAL_ANSWER_ACTION in text
        regex = (
            r"Action\s*\d*\s*:[\s]*(.*?)[\s]*Action\s*\d*\s*Input\s*\d*\s*:[\s]*(.*)"
        )
        action_match = re.search(regex, text, re.DOTALL)
        if action_match:
            if includes_answer:
                msg = f"{FINAL_ANSWER_AND_PARSABLE_ACTION_ERROR_MESSAGE}: {text}"
                raise OutputParserException(msg)
            action = action_match.group(1).strip()
            action_input = action_match.group(2)
            tool_input = action_input.strip(" ")
            tool_input = tool_input.strip('"')

            return AgentAction(action, tool_input, text)

        if includes_answer:
            return AgentFinish(
                {"output": text.rsplit(FINAL_ANSWER_ACTION, maxsplit=1)[-1].strip()},
                text,
            )

        if not re.search(r"Action\s*\d*\s*:[\s]*(.*?)", text, re.DOTALL):
            msg = f"Could not parse LLM output: `{text}`"
            raise OutputParserException(
                msg,
                observation=MISSING_ACTION_AFTER_THOUGHT_ERROR_MESSAGE,
                llm_output=text,
                send_to_llm=True,
            )
        if not re.search(
            r"[\s]*Action\s*\d*\s*Input\s*\d*\s*:[\s]*(.*)",
            text,
            re.DOTALL,
        ):
            msg = f"Could not parse LLM output: `{text}`"
            raise OutputParserException(
                msg,
                observation=MISSING_ACTION_INPUT_AFTER_ACTION_ERROR_MESSAGE,
                llm_output=text,
                send_to_llm=True,
            )
        msg = f"Could not parse LLM output: `{text}`"
        raise OutputParserException(msg)