我没法让这个工作起来：

from langchain_community.agent_toolkits import PlayWrightBrowserToolkit
from langchain_openai import ChatOpenAI
from langchain.agents import create_agent
import asyncio
import nest_asyncio
nest_asyncio.apply()

from langchain_community.tools.playwright.utils import (
    create_sync_playwright_browser, 
)


def main():
    sync_browser = create_sync_playwright_browser(headless=False)
    toolkit = PlayWrightBrowserToolkit.from_browser(sync_browser=sync_browser)
    tools = toolkit.get_tools()



    model = ChatOpenAI(model="gpt-4o", temperature=0)

    agent_chain = create_agent(model=model, tools=tools)

    result = agent_chain.invoke(
        {"messages": [("user", "What are the headers on langchain.com?")]}
    )
    print(result)


if __name__ == "__main__":

    main()

我遇到的错误是

File "C:\Users\paulo\anaconda3\envs\estee\Lib\site-packages\playwright_impl_sync_base.py", 
line 113, in _sync self._dispatcher_fiber.switch() greenlet.error: 
Cannot switch to a different thread Current: 
<greenlet.greenlet object at 0x000001CA8AE7F900 
(otid=0x000001CA89E17180) current active started main> 
Expected: 
<greenlet.greenlet object at 0x000001CA89E42100 
(otid=0x000001CA8A3BC060) suspended active started main>

我的目标只是让langchain和 playwright有一个能运行的Hello World示例；浏览器是同步还是异步对我来说都无所谓，我只想要一个最基本的可正常工作的实现。我一开始尝试了异步浏览器，但也没成功。

能不能请人帮忙？

解决方案

我拿到了你的代码，并把它转换成 async 版本，在 Linux Mint 上对我可用（基于 Ubuntu 24.02），使用 langchain 1.2.x，不是 0.3.x。

如果在你的电脑上运行不起来，可能只是Windows的问题。

我用 Ollama 代替 OpenAI 进行了测试。

我在终端里把它作为脚本运行（使用Python 3.13），而不是在Jupyter中作为代码运行。

它没有抛出任何错误，能从代理那里得到响应，但它说在langchain.com上找不到头部信息。

# --- info ---

import langchain
import langchain_community

print("langchain:", langchain.__version__)
print("langchain_community:", langchain_community.__version__)

# --- code ---

from langchain_community.agent_toolkits import PlayWrightBrowserToolkit
from langchain_community.tools.playwright.utils import create_async_playwright_browser
from langchain.agents import create_agent

# from langchain_openai import ChatOpenAI
from langchain_ollama import ChatOllama

# it needs it to run async browser
import nest_asyncio
nest_asyncio.apply()


async def main():  # <-- async
    async_browser = create_async_playwright_browser()
    toolkit = PlayWrightBrowserToolkit.from_browser(async_browser=async_browser)
    tools = toolkit.get_tools()

    print("--- tools ---")
    for item in tools:
        print(item.name)

    # model = ChatOpenAI(model="gpt-4o", temperature=0)
    model = ChatOllama(model="llama3.2", temperature=0)

    agent_chain = create_agent(model=model, tools=tools)

    result = await agent_chain.ainvoke(  # <-- await, ainvoke
        {"messages": [("user", "What are the headers on langchain.com?")]}
    )

    print("--- result ---")
    print(result)

    print("--- messages ---")
    for item in result["messages"]:
        print("type:", item.type)
        print("name:", item.name)
        print("content:", item.content)
        print("---")


if __name__ == "__main__":
    # main()
    import asyncio
    asyncio.run(main())

结果：

langchain: 1.2.13
langchain_community: 0.4.1
--- tools ---
click_element
navigate_browser
previous_webpage
extract_text
extract_hyperlinks
get_elements
current_webpage
--- result ---
{'messages': [HumanMessage(content='What are the headers on langchain.com?', additional_kwargs={}, response_metadata={}, id='c2575d91-99d8-48bf-afea-7c24d6b1fc16'), AIMessage(content='', additional_kwargs={}, response_metadata={'model': 'llama3.2', 'created_at': '2026-03-31T20:28:18.548216398Z', 'done': True, 'done_reason': 'stop', 'total_duration': 8932239195, 'load_duration': 121650058, 'prompt_eval_count': 425, 'prompt_eval_duration': 7491245727, 'eval_count': 16, 'eval_duration': 1289860413, 'logprobs': None, 'model_name': 'llama3.2', 'model_provider': 'ollama'}, id='lc_run--019d4595-0e0b-79d2-ac5e-623fcbf23c14-0', tool_calls=[{'name': 'get_elements', 'args': {'selector': '*'}, 'id': '516c49b6-28c1-427f-b0da-2d66274d7d50', 'type': 'tool_call'}], invalid_tool_calls=[], usage_metadata={'input_tokens': 425, 'output_tokens': 16, 'total_tokens': 441}), ToolMessage(content='[]', name='get_elements', id='0a4f9c45-f3eb-43ee-b182-ae610d903450', tool_call_id='516c49b6-28c1-427f-b0da-2d66274d7d50'), AIMessage(content="Based on the output from the tool call, it appears that the headers on langchain.com are not explicitly listed. The tool call `get_elements` with the selector `*` returns an empty list, indicating that the headers are not available or are not present on the page.\n\nHowever, I can suggest that you try checking the website's documentation or contact support for more information on the available headers or API endpoints.", additional_kwargs={}, response_metadata={'model': 'llama3.2', 'created_at': '2026-03-31T20:28:27.005448701Z', 'done': True, 'done_reason': 'stop', 'total_duration': 8350693341, 'load_duration': 153406746, 'prompt_eval_count': 93, 'prompt_eval_duration': 1321625016, 'eval_count': 84, 'eval_duration': 6851252575, 'logprobs': None, 'model_name': 'llama3.2', 'model_provider': 'ollama'}, id='lc_run--019d4595-315d-70b0-b9f3-8c5595de86bf-0', tool_calls=[], invalid_tool_calls=[], usage_metadata={'input_tokens': 93, 'output_tokens': 84, 'total_tokens': 177})]}
--- messages ---
type: human
name: None
content: What are the headers on langchain.com?
---
type: ai
name: None
content:
---
type: tool
name: get_elements
content: []
---
type: ai
name: None
content: Based on the output from the tool call, it appears that the headers on langchain.com are not explicitly listed. The tool call `get_elements` with the selector `*` returns an empty list, indicating that the headers are not available or are not present on the page.