How can multiple buttons in Streamlit call the same Playwright page object?

[ffsxsy]

hi, I’m a novice in using Streamlit.need your help!

My operating environment is:
Windows 11, Python 3.13
Streamlit = 1.41.1
Playwright = 1.49.1

Now, using Streamlit, I need to create three buttons. When the first button is pressed, it should use Playwright to open a web page in the browser. When the second button is pressed, it should use Playwright to take a screenshot of the web page. When the third button is pressed, it should use Playwright to close the window.

The problem I encounter is how to call the same page object when the GUI is re - run.
here is my code:

import streamlit as st
from playwright.async_api import async_playwright
import asyncio
import nest_asyncio
# apply nest_asyncio
nest_asyncio.apply()
# switch to ProactorEventLoop
if st.runtime.exists():
    asyncio.set_event_loop_policy(asyncio.WindowsProactorEventLoopPolicy())

# initialize session_state
if "browser" not in st.session_state:
    st.session_state.browser = None
if "page" not in st.session_state:
    st.session_state.page = None

async def open_browser():
    playwright = await async_playwright().start()
    st.session_state.browser = await playwright.chromium.launch(headless=False)
    st.session_state.page = await st.session_state.browser.new_page()
    await st.session_state.page.goto("https://www.baidu.com")
    st.success("webpage opened")

async def take_screenshot():
    if st.session_state.page:
        await st.session_state.page.screenshot(path="screenshot.png")
        st.success("snapshot saved as screenshot.png")
    else:
        st.error("please open the webpage first")

async def close_browser():
    if st.session_state.browser:
        await st.session_state.browser.close()
        st.session_state.browser = None
        st.session_state.page = None
        st.success("browser closed")
    else:
        st.error("browser not opened")

# Streamlit gui
st.title("Playwright and Streamlit integration")

if st.button("open"):
    asyncio.run(open_browser())

if st.button("snapshot"):
    asyncio.run(take_screenshot())

if st.button("close"):
    asyncio.run(close_browser())

when run the code, after click the “open” button, the target page opened as expected, but when i click the “snapshot” button, the streamlit page keep “running”???
anybody can help?

[Encrypt]

Using multiprocessing is a better approach when working with Playwright and Streamlit, especially when you need the Playwright code to run in a separate CPU process. This separation ensures that both the Streamlit and Playwright processes are independent of each other, reducing the risk of threading issues or deadlocks. They can then communicate with each other via Inter Process Communication (IPC), which allows for safer and more efficient data exchange between the two processes. Below is an example code you can use.

import streamlit as st
from multiprocessing import Process, Queue


# Initialize session_state
if "browser_process" not in st.session_state:
    st.session_state.browser_process = None
if "command_queue" not in st.session_state:
    st.session_state.command_queue = Queue()
if "response_queue" not in st.session_state:
    st.session_state.response_queue = Queue()

def playwright_process(command_queue, response_queue):
    from playwright.sync_api import sync_playwright
    with sync_playwright() as playwright:
        browser = playwright.chromium.launch(headless=False)
        page = browser.new_page()
        while True:
            command = command_queue.get()
            if command == "open":
                page.goto("https://www.baidu.com")
                response_queue.put("Webpage opened")
            elif command == "screenshot":
                page.screenshot(path="screenshot.png")
                response_queue.put("Snapshot saved as screenshot.png")
            elif command == "close":
                browser.close()
                response_queue.put("Browser closed")
                break

def open_browser():
    if st.session_state.browser_process is None:
        st.session_state.browser_process = Process(target=playwright_process, args=(st.session_state.command_queue, st.session_state.response_queue))
        st.session_state.browser_process.start()
        st.session_state.command_queue.put("open")
        response = st.session_state.response_queue.get()
        st.success(response)
    else:
        st.error("Browser already opened")

def take_screenshot():
    if st.session_state.browser_process is not None:
        st.session_state.command_queue.put("screenshot")
        response = st.session_state.response_queue.get()
        st.success(response)
    else:
        st.error("Please open the browser first")

def close_browser():
    if st.session_state.browser_process is not None:
        st.session_state.command_queue.put("close")
        response = st.session_state.response_queue.get()
        st.session_state.browser_process.join()
        st.session_state.browser_process = None
        st.success(response)
    else:
        st.error("Browser not opened")

# Streamlit GUI
st.title("Playwright and Streamlit Integration")

# Streamlit buttons to trigger the functions
if st.button("Open Browser"):
    open_browser()

if st.button("Take Screenshot"):
    take_screenshot()

if st.button("Close Browser"):
    close_browser()