处理解析错误

偶尔 LLM 无法确定要采取的步骤，因为其输出的格式不正确，无法被输出解析器处理。在这种情况下，默认情况下代理会报错。但是您可以使用 handle_parsing_errors 轻松控制此功能！让我们来看看如何操作。

设置

from langchain import (
    OpenAI,
    LLMMathChain,
    SerpAPIWrapper,
    SQLDatabase,
    SQLDatabaseChain,
)
from langchain.agents import initialize_agent, Tool
from langchain.agents import AgentType
from langchain.chat_models import ChatOpenAI
from langchain.agents.types import AGENT_TO_CLASS

search = SerpAPIWrapper()
tools = [
    Tool(
        name="Search",
        func=search.run,
        description="useful for when you need to answer questions about current events. You should ask targeted questions",
    ),
]

Error

In this scenario, the agent will error (because it fails to output an Action string)

mrkl = initialize_agent(
    tools,
    ChatOpenAI(temperature=0),
    agent=AgentType.CHAT_ZERO_SHOT_REACT_DESCRIPTION,
    verbose=True,
)

mrkl.run("Who is Leo DiCaprio's girlfriend? No need to add Action")

> Entering new AgentExecutor chain...



---------------------------------------------------------------------------

IndexError                                Traceback (most recent call last)

File ~/workplace/langchain/langchain/agents/chat/output_parser.py:21, in ChatOutputParser.parse(self, text)
     20 try:
---> 21     action = text.split("```")[1]
     22     response = json.loads(action.strip())


IndexError: list index out of range


During handling of the above exception, another exception occurred:


OutputParserException                     Traceback (most recent call last)

Cell In[4], line 1
----> 1 mrkl.run("Who is Leo DiCaprio's girlfriend? No need to add Action")


File ~/workplace/langchain/langchain/chains/base.py:236, in Chain.run(self, callbacks, *args, **kwargs)
    234     if len(args) != 1:
    235         raise ValueError("`run` supports only one positional argument.")
--> 236     return self(args[0], callbacks=callbacks)[self.output_keys[0]]
    238 if kwargs and not args:
    239     return self(kwargs, callbacks=callbacks)[self.output_keys[0]]


File ~/workplace/langchain/langchain/chains/base.py:140, in Chain.__call__(self, inputs, return_only_outputs, callbacks)
    138 except (KeyboardInterrupt, Exception) as e:
    139     run_manager.on_chain_error(e)
--> 140     raise e
    141 run_manager.on_chain_end(outputs)
    142 return self.prep_outputs(inputs, outputs, return_only_outputs)


File ~/workplace/langchain/langchain/chains/base.py:134, in Chain.__call__(self, inputs, return_only_outputs, callbacks)
    128 run_manager = callback_manager.on_chain_start(
    129     {"name": self.__class__.__name__},
    130     inputs,
    131 )
    132 try:
    133     outputs = (
--> 134         self._call(inputs, run_manager=run_manager)
    135         if new_arg_supported
    136         else self._call(inputs)
    137     )
    138 except (KeyboardInterrupt, Exception) as e:
    139     run_manager.on_chain_error(e)


File ~/workplace/langchain/langchain/agents/agent.py:947, in AgentExecutor._call(self, inputs, run_manager)
    945 # We now enter the agent loop (until it returns something).
    946 while self._should_continue(iterations, time_elapsed):
--> 947     next_step_output = self._take_next_step(
    948         name_to_tool_map,
    949         color_mapping,
    950         inputs,
    951         intermediate_steps,
    952         run_manager=run_manager,
    953     )
    954     if isinstance(next_step_output, AgentFinish):
    955         return self._return(
    956             next_step_output, intermediate_steps, run_manager=run_manager
    957         )


File ~/workplace/langchain/langchain/agents/agent.py:773, in AgentExecutor._take_next_step(self, name_to_tool_map, color_mapping, inputs, intermediate_steps, run_manager)
    771     raise_error = False
    772 if raise_error:
--> 773     raise e
    774 text = str(e)
    775 if isinstance(self.handle_parsing_errors, bool):


File ~/workplace/langchain/langchain/agents/agent.py:762, in AgentExecutor._take_next_step(self, name_to_tool_map, color_mapping, inputs, intermediate_steps, run_manager)
    756 """Take a single step in the thought-action-observation loop.
    757 
    758 Override this to take control of how the agent makes and acts on choices.
    759 """
    760 try:
    761     # Call the LLM to see what to do.
--> 762     output = self.agent.plan(
    763         intermediate_steps,
    764         callbacks=run_manager.get_child() if run_manager else None,
    765         **inputs,
    766     )
    767 except OutputParserException as e:
    768     if isinstance(self.handle_parsing_errors, bool):


File ~/workplace/langchain/langchain/agents/agent.py:444, in Agent.plan(self, intermediate_steps, callbacks, **kwargs)
    442 full_inputs = self.get_full_inputs(intermediate_steps, **kwargs)
    443 full_output = self.llm_chain.predict(callbacks=callbacks, **full_inputs)
--> 444 return self.output_parser.parse(full_output)


File ~/workplace/langchain/langchain/agents/chat/output_parser.py:26, in ChatOutputParser.parse(self, text)
     23     return AgentAction(response["action"], response["action_input"], text)
     25 except Exception:
---> 26     raise OutputParserException(f"Could not parse LLM output: {text}")


OutputParserException: Could not parse LLM output: I'm sorry, but I cannot provide an answer without an Action. Please provide a valid Action in the format specified above.

Default error handling

Handle errors with Invalid or incomplete response

mrkl = initialize_agent(
    tools,
    ChatOpenAI(temperature=0),
    agent=AgentType.CHAT_ZERO_SHOT_REACT_DESCRIPTION,
    verbose=True,
    handle_parsing_errors=True,
)

mrkl.run("Who is Leo DiCaprio's girlfriend? No need to add Action")

> Entering new AgentExecutor chain...

Observation: Invalid or incomplete response
Thought:
Observation: Invalid or incomplete response
Thought:Search for Leo DiCaprio's current girlfriend
Action:
```
{
  "action": "Search",
  "action_input": "Leo DiCaprio current girlfriend"
}
```

Observation: Just Jared on Instagram: “Leonardo DiCaprio & girlfriend Camila Morrone couple up for a lunch date!
Thought:Camila Morrone is currently Leo DiCaprio's girlfriend
Final Answer: Camila Morrone

> Finished chain.





'Camila Morrone'

Custom Error Message

You can easily customize the message to use when there are parsing errors

mrkl = initialize_agent(
    tools,
    ChatOpenAI(temperature=0),
    agent=AgentType.CHAT_ZERO_SHOT_REACT_DESCRIPTION,
    verbose=True,
    handle_parsing_errors="Check your output and make sure it conforms!",
)

mrkl.run("Who is Leo DiCaprio's girlfriend? No need to add Action")

> Entering new AgentExecutor chain...

Observation: Could not parse LLM output: I'm sorry, but I canno
Thought:I need to use the Search tool to find the answer to the question.
Action:
```
{
  "action": "Search",
  "action_input": "Who is Leo DiCaprio's girlfriend?"
}
```

Observation: DiCaprio broke up with girlfriend Camila Morrone, 25, in the summer of 2022, after dating for four years. He's since been linked to another famous supermodel – Gigi Hadid. The power couple were first supposedly an item in September after being spotted getting cozy during a party at New York Fashion Week.
Thought:The answer to the question is that Leo DiCaprio's current girlfriend is Gigi Hadid. 
Final Answer: Gigi Hadid.

> Finished chain.





'Gigi Hadid.'

Custom Error Function

You can also customize the error to be a function that takes the error in and outputs a string.

def _handle_error(error) -> str:
    return str(error)[:50]


mrkl = initialize_agent(
    tools,
    ChatOpenAI(temperature=0),
    agent=AgentType.CHAT_ZERO_SHOT_REACT_DESCRIPTION,
    verbose=True,
    handle_parsing_errors=_handle_error,
)

mrkl.run("Who is Leo DiCaprio's girlfriend? No need to add Action")

> Entering new AgentExecutor chain...

Observation: Could not parse LLM output: I'm sorry, but I canno
Thought:I need to use the Search tool to find the answer to the question.
Action:
```
{
  "action": "Search",
  "action_input": "Who is Leo DiCaprio's girlfriend?"
}
```

Observation: DiCaprio broke up with girlfriend Camila Morrone, 25, in the summer of 2022, after dating for four years. He's since been linked to another famous supermodel – Gigi Hadid. The power couple were first supposedly an item in September after being spotted getting cozy during a party at New York Fashion Week.
Thought:The current girlfriend of Leonardo DiCaprio is Gigi Hadid. 
Final Answer: Gigi Hadid.

> Finished chain.





'Gigi Hadid.'