PlayWrightBrowserToolkit example does not run properly

[vivek-alhat]

I am trying to run the PlayWrightBrowserToolkit using React agent but it fails and gives below error:

Action: navigate_browser
Action Input: "https://python.langchain.com"Navigating to https://python.langchain.com returned status code 200I have successfully navigated to the website. Now, I need to extract the headers from the page, which typically include elements like <h1>, <h2>, <h3>, etc. 

Action: extract_text
Action Input: NoneTraceback (most recent call last):
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain_core\tools\base.py", line 806, in arun
    raise error_to_raise
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain_core\tools\base.py", line 758, in arun
    tool_args, tool_kwargs = self._to_args_and_kwargs(tool_input)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain_core\tools\base.py", line 574, in _to_args_and_kwargs
    tool_input = self._parse_input(tool_input)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain_core\tools\base.py", line 506, in _parse_input
    key_ = next(iter(get_fields(input_args).keys()))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "c:\Users\vivek\Documents\Personal\learnings\AI\corrective-rag\web-browser-tool-test.py", line 32, in <module>
    loop.run_until_complete(main())
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\asyncio\base_events.py", line 685, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "c:\Users\vivek\Documents\Personal\learnings\AI\corrective-rag\web-browser-tool-test.py", line 23, in main
    response = await agent_executor.ainvoke(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain\chains\base.py", line 221, in ainvoke
    raise e
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain\chains\base.py", line 212, in ainvoke
    await self._acall(inputs, run_manager=run_manager)
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain\agents\agent.py", line 1678, in _acall
    next_step_output = await self._atake_next_step(
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain\agents\agent.py", line 1472, in _atake_next_step
    [
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain\agents\agent.py", line 1556, in _aiter_next_step
    result = await asyncio.gather(
             ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\vivek\AppData\Local\Programs\Python\Python312\Lib\site-packages\langchain\agents\agent.py", line 1589, in _aperform_agent_action
    observation = await tool.arun(
                  ^^^^^^^^^^^^^^^^
RuntimeError: coroutine raised StopIteration```

Here's my code:

```from langchain_community.tools.playwright.utils import create_async_playwright_browser
from langchain_community.agent_toolkits import PlayWrightBrowserToolkit
from langchain.agents import AgentExecutor, create_react_agent
from langchain_openai import ChatOpenAI
from langchain import hub
import asyncio
import dotenv

dotenv.load_dotenv(".env")

async_browser = create_async_playwright_browser()
toolkit = PlayWrightBrowserToolkit.from_browser(async_browser=async_browser)
tools = toolkit.get_tools()

llm = ChatOpenAI(model="gpt-4o-mini")

prompt = hub.pull("hwchase17/react")
agent = create_react_agent(llm, tools, prompt)
agent_executor = AgentExecutor(agent=agent, tools=tools, verbose=True)


async def main():
    response = await agent_executor.ainvoke(
        {"input": "What are the headers on python.langchain.com?"}
    )
    print(response)


import asyncio

loop = asyncio.get_event_loop()
loop.run_until_complete(main())

[dosubot[bot]]

Hey @vivek-alhat 👋, I'm here to help you with your coding issues and questions. If you need any assistance with bug fixes, code improvements, or anything else, feel free to ask!

I found a similar unsolved discussion regarding the use of PlayWright with LangChain ^[1]. Additionally, a common cause of the StopIteration error in LangChain's tool execution is related to the input parsing mechanism, where the tool might not be receiving the expected input format.

In your case, the error occurs during the extract_text action. This might be due to the tool expecting specific input arguments that are not being provided or parsed correctly. Here are a few steps you can take to troubleshoot and potentially resolve the issue:

1. Check Tool Input Requirements: Ensure that the extract_text tool is being invoked with the correct input format. It might require specific arguments or a different way to handle inputs.

2. Update Dependencies: Make sure all your dependencies, including LangChain and Playwright, are up to date. Sometimes, issues arise from version mismatches.

3. Debug Input Parsing: Add logging or print statements to check what inputs are being passed to the tool and how they are being parsed. This can help identify if the input format is incorrect.

4. Review Documentation: Check the LangChain documentation or examples for any updates or changes in how tools should be used, especially if there have been recent updates to the library.

If these steps do not resolve the issue, you might need to delve deeper into the specific implementation of the extract_text tool to understand its input requirements and adjust your code accordingly.

To continue talking to Dosu, mention @dosu.

[vivek-alhat]

@dosu I checked LangSmith trace and it seems the Action Input is going as None to extract_text tool. Why is that?

[dosubot[bot]]

The Action Input is going as None to the extract_text tool because the output from the language model does not match the expected format. Specifically, the output is missing the "Action Input:" part after the "Action:" as indicated by the error message MISSING_ACTION_INPUT_AFTER_ACTION_ERROR_MESSAGE. The parser expects the output to include both "Action:" and "Action Input:" sections, and if the "Action Input:" is missing, it raises an OutputParserException with the message "Invalid Format: Missing 'Action Input:' after 'Action:'" ^[1].

To continue talking to Dosu, mention @dosu.