self_ask.py — langchain Source File

Source Code

from collections.abc import Sequence

from langchain_core.agents import AgentAction, AgentFinish
from langchain_core.exceptions import OutputParserException
from typing_extensions import override

from langchain_classic.agents.agent import AgentOutputParser


class SelfAskOutputParser(AgentOutputParser):
    """Parses self-ask style LLM calls.

    Expects output to be in one of two formats.

    If the output signals that an action should be taken,
    should be in the below format. This will result in an AgentAction
    being returned.

    ```
    Thoughts go here...
    Follow up: what is the temperature in SF?
    ```

    If the output signals that a final answer should be given,
    should be in the below format. This will result in an AgentFinish
    being returned.

    ```
    Thoughts go here...
    So the final answer is: The temperature is 100 degrees
    ```

    """

    followups: Sequence[str] = ("Follow up:", "Followup:")
    finish_string: str = "So the final answer is: "

    @override
    def parse(self, text: str) -> AgentAction | AgentFinish:
        last_line = text.rsplit("\n", maxsplit=1)[-1]
        if not any(follow in last_line for follow in self.followups):
            if self.finish_string not in last_line:
                msg = f"Could not parse output: {text}"
                raise OutputParserException(msg)
            return AgentFinish({"output": last_line[len(self.finish_string) :]}, text)

        after_colon = text.rsplit(":", maxsplit=1)[-1].strip()
        return AgentAction("Intermediate Answer", after_colon, text)

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