Running Agent as an Iterator

It can be useful to run the agent as an iterator, to add human-in-the-loop checks as needed.

To demonstrate the AgentExecutorIterator functionality, we will set up a problem where an Agent must:

• Retrieve three prime numbers from a Tool
• Multiply these together.

In this simple problem we can demonstrate adding some logic to verify intermediate steps by checking whether their outputs are prime.

from langchain.agents import AgentType, initialize_agent
from langchain.chains import LLMMathChain
from langchain_core.pydantic_v1 import BaseModel, Field
from langchain_core.tools import Tool
from langchain_openai import ChatOpenAI

API Reference:

• AgentType
• initialize_agent
• LLMMathChain
• Tool
• ChatOpenAI

%pip install --upgrade --quiet  numexpr

# need to use GPT-4 here as GPT-3.5 does not understand, however hard you insist, that
# it should use the calculator to perform the final calculation
llm = ChatOpenAI(temperature=0, model="gpt-4")
llm_math_chain = LLMMathChain.from_llm(llm=llm, verbose=True)

Define tools which provide:

• The nth prime number (using a small subset for this example)

• The LLMMathChain to act as a calculator

primes = {998: 7901, 999: 7907, 1000: 7919}


class CalculatorInput(BaseModel):
    question: str = Field()


class PrimeInput(BaseModel):
    n: int = Field()


def is_prime(n: int) -> bool:
    if n <= 1 or (n % 2 == 0 and n > 2):
        return False
    for i in range(3, int(n**0.5) + 1, 2):
        if n % i == 0:
            return False
    return True


def get_prime(n: int, primes: dict = primes) -> str:
    return str(primes.get(int(n)))


async def aget_prime(n: int, primes: dict = primes) -> str:
    return str(primes.get(int(n)))


tools = [
    Tool(
        name="GetPrime",
        func=get_prime,
        description="A tool that returns the `n`th prime number",
        args_schema=PrimeInput,
        coroutine=aget_prime,
    ),
    Tool.from_function(
        func=llm_math_chain.run,
        name="Calculator",
        description="Useful for when you need to compute mathematical expressions",
        args_schema=CalculatorInput,
        coroutine=llm_math_chain.arun,
    ),
]

Construct the agent. We will use OpenAI Functions agent here.

from langchain import hub

# Get the prompt to use - you can modify this!
# You can see the full prompt used at: https://smith.langchain.com/hub/hwchase17/openai-functions-agent
prompt = hub.pull("hwchase17/openai-functions-agent")

from langchain.agents import create_openai_functions_agent

agent = create_openai_functions_agent(llm, tools, prompt)

API Reference:

• create_openai_functions_agent

from langchain.agents import AgentExecutor

agent_executor = AgentExecutor(agent=agent, tools=tools, verbose=True)

API Reference:

• AgentExecutor

Run the iteration and perform a custom check on certain steps:

question = "What is the product of the 998th, 999th and 1000th prime numbers?"

for step in agent_executor.iter({"input": question}):
    if output := step.get("intermediate_step"):
        action, value = output[0]
        if action.tool == "GetPrime":
            print(f"Checking whether {value} is prime...")
            assert is_prime(int(value))
        # Ask user if they want to continue
        _continue = input("Should the agent continue (Y/n)?:\n") or "Y"
        if _continue.lower() != "y":
            break

> Entering new AgentExecutor chain...

Invoking: `GetPrime` with `{'n': 998}`


7901Checking whether 7901 is prime...
Should the agent continue (Y/n)?:
y

Invoking: `GetPrime` with `{'n': 999}`


7907Checking whether 7907 is prime...
Should the agent continue (Y/n)?:
y

Invoking: `GetPrime` with `{'n': 1000}`


7919Checking whether 7919 is prime...
Should the agent continue (Y/n)?:
y

Invoking: `Calculator` with `{'question': '7901 * 7907 * 7919'}`




> Entering new LLMMathChain chain...
7901 * 7907 * 7919```text
7901 * 7907 * 7919

...numexpr.evaluate("7901 7907 7919")...  Answer: 494725326233 > Finished chain. Answer: 494725326233Should the agent continue (Y/n)?: y The product of the 998th, 999th and 1000th prime numbers is 494,725,326,233.

> Finished chain.