Source code for langchain.agents.react.output_parser

import re
from typing import Union

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

from langchain.agents.agent import AgentOutputParser

[docs]class ReActOutputParser(AgentOutputParser): """Output parser for the ReAct agent."""
[docs] def parse(self, text: str) -> Union[AgentAction, AgentFinish]: action_prefix = "Action: " if not text.strip().split("\n")[-1].startswith(action_prefix): raise OutputParserException(f"Could not parse LLM Output: {text}") action_block = text.strip().split("\n")[-1] action_str = action_block[len(action_prefix) :] # Parse out the action and the directive. re_matches ="(.*?)\[(.*?)\]", action_str) if re_matches is None: raise OutputParserException( f"Could not parse action directive: {action_str}" ) action, action_input =, if action == "Finish": return AgentFinish({"output": action_input}, text) else: return AgentAction(action, action_input, text)
@property def _type(self) -> str: return "react"