Source code for langchain.agents.structured_chat.output_parser
from __future__ import annotations
import json
import logging
import re
from typing import Optional, Pattern, Union
from langchain_core.agents import AgentAction, AgentFinish
from langchain_core.exceptions import OutputParserException
from langchain_core.language_models import BaseLanguageModel
from langchain_core.pydantic_v1 import Field
from langchain.agents.agent import AgentOutputParser
from langchain.agents.structured_chat.prompt import FORMAT_INSTRUCTIONS
from langchain.output_parsers import OutputFixingParser
logger = logging.getLogger(__name__)
[docs]
class StructuredChatOutputParser(AgentOutputParser):
"""Output parser for the structured chat agent."""
format_instructions: str = FORMAT_INSTRUCTIONS
"""Default formatting instructions"""
pattern: Pattern = re.compile(r"```(?:json\s+)?(\W.*?)```", re.DOTALL)
"""Regex pattern to parse the output."""
[docs]
def parse(self, text: str) -> Union[AgentAction, AgentFinish]:
try:
action_match = self.pattern.search(text)
if action_match is not None:
response = json.loads(action_match.group(1).strip(), strict=False)
if isinstance(response, list):
# gpt turbo frequently ignores the directive to emit a single action
logger.warning("Got multiple action responses: %s", response)
response = response[0]
if response["action"] == "Final Answer":
return AgentFinish({"output": response["action_input"]}, text)
else:
return AgentAction(
response["action"], response.get("action_input", {}), text
)
else:
return AgentFinish({"output": text}, text)
except Exception as e:
raise OutputParserException(f"Could not parse LLM output: {text}") from e
@property
def _type(self) -> str:
return "structured_chat"
[docs]
class StructuredChatOutputParserWithRetries(AgentOutputParser):
"""Output parser with retries for the structured chat agent."""
base_parser: AgentOutputParser = Field(default_factory=StructuredChatOutputParser)
"""The base parser to use."""
output_fixing_parser: Optional[OutputFixingParser] = None
"""The output fixing parser to use."""
[docs]
def parse(self, text: str) -> Union[AgentAction, AgentFinish]:
try:
if self.output_fixing_parser is not None:
parsed_obj: Union[AgentAction, AgentFinish] = (
self.output_fixing_parser.parse(text)
)
else:
parsed_obj = self.base_parser.parse(text)
return parsed_obj
except Exception as e:
raise OutputParserException(f"Could not parse LLM output: {text}") from e
[docs]
@classmethod
def from_llm(
cls,
llm: Optional[BaseLanguageModel] = None,
base_parser: Optional[StructuredChatOutputParser] = None,
) -> StructuredChatOutputParserWithRetries:
if llm is not None:
base_parser = base_parser or StructuredChatOutputParser()
output_fixing_parser: OutputFixingParser = OutputFixingParser.from_llm(
llm=llm, parser=base_parser
)
return cls(output_fixing_parser=output_fixing_parser)
elif base_parser is not None:
return cls(base_parser=base_parser)
else:
return cls()
@property
def _type(self) -> str:
return "structured_chat_with_retries"
