LCEL

lcel.py

# the prompt is pulled from the LangSmith Hub which hosts many different prompts
prompt = hub.pull("hwchase17/self-ask-with-search")
llm = OpenAI(temperature=0)

# provide the LM with useful tools
search = SerpAPIWrapper()
tools =  Tool( name="Intermediate Answer", func=search.run, description="useful for when you need to ask with search")]

llm_with_stop = llm.bind(stop=["\nIntermediate answer:"])
agent = (
{
  "input": lambda x: x["input"],
   # Use some custom observation_prefix/llm_prefix for formatting 
   "agent_scratchpad": lambda x: format_log_to_str( x["intermediate_steps"],         
                    observation_prefix="\nIntermediate answer: ",llm_prefix="",), }
| prompt
| llm_with_stop
| SelfAskOutputParser())

agent_executor.invoke({"input": "What is the hometown of the reigning men's U.S. Open champion?"})