Source code for langchain.agents.output_parsers.react_json_single_input
import json
import re
from re import Pattern
from typing import Union
from langchain_core.agents import AgentAction, AgentFinish
from langchain_core.exceptions import OutputParserException
from langchain.agents.agent import AgentOutputParser
from langchain.agents.chat.prompt import FORMAT_INSTRUCTIONS
FINAL_ANSWER_ACTION = "Final Answer:"
[docs]
class ReActJsonSingleInputOutputParser(AgentOutputParser):
"""Parses ReAct-style LLM calls that have a single tool input in json format.
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.
```
Thought: agent thought here
Action:
```
{
"action": "search",
"action_input": "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.
```
Thought: agent thought here
Final Answer: The temperature is 100 degrees
```
"""
pattern: Pattern = re.compile(r"^.*?`{3}(?:json)?\n?(.*?)`{3}.*?$", re.DOTALL)
"""Regex pattern to parse the output."""
[docs]
def parse(self, text: str) -> Union[AgentAction, AgentFinish]:
includes_answer = FINAL_ANSWER_ACTION in text
try:
found = self.pattern.search(text)
if not found:
# Fast fail to parse Final Answer.
msg = "action not found"
raise ValueError(msg)
action = found.group(1)
response = json.loads(action.strip())
includes_action = "action" in response
if includes_answer and includes_action:
msg = (
"Parsing LLM output produced a final answer "
f"and a parse-able action: {text}"
)
raise OutputParserException(msg)
return AgentAction(
response["action"],
response.get("action_input", {}),
text,
)
except Exception as e:
if not includes_answer:
msg = f"Could not parse LLM output: {text}"
raise OutputParserException(msg) from e
output = text.split(FINAL_ANSWER_ACTION)[-1].strip()
return AgentFinish({"output": output}, text)
@property
def _type(self) -> str:
return "react-json-single-input"