如何在FastAPI应用的函数中运行Playwright Asyncio代码？

问题描述 #

我正在用FastAPI和Playwright构建API，不清楚如何将Playwright的异步代码整合到FastAPI的接口函数中。现有两段示例代码：

Playwright异步示例代码 #

import asyncio
from playwright.async_api import async_playwright

async def main():
    async with async_playwright() as p:
        browser = await p.chromium.launch()
        page = await browser.new_page()
        await page.goto("http://playwright.dev")
        print(await page.title())
        await browser.close()

asyncio.run(main())

FastAPI示例代码 #

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def read_root():
    return {"Hello": "World"}

@app.get("/playwright")
def run_playwright():
    return "Results from running Playwright"

需要实现的是在FastAPI的/playwright接口函数内运行Playwright的异步代码。

解决方案 #

1. 将FastAPI接口改为异步函数 #

FastAPI原生支持异步端点，只需把接口函数定义改为async def，就能直接在函数内部使用await调用异步操作，无需手动启动新的事件循环。

2. 整合Playwright异步逻辑到接口 #

直接在异步接口函数内编写Playwright的异步代码逻辑，不需要使用asyncio.run()（FastAPI会自动管理事件循环）。

基础整合代码示例

from fastapi import FastAPI
from playwright.async_api import async_playwright

app = FastAPI()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

@app.get("/playwright")
async def run_playwright():
    async with async_playwright() as p:
        browser = await p.chromium.launch()
        page = await browser.new_page()
        await page.goto("http://playwright.dev")
        page_title = await page.title()
        await browser.close()
    return {"page_title": page_title}

3. 优化：复用浏览器实例（提升性能） #

每次请求都启动和关闭浏览器会大幅降低接口性能，建议在应用启动时初始化一个全局浏览器实例，应用关闭时再销毁：

from fastapi import FastAPI
from playwright.async_api import async_playwright, Browser

app = FastAPI()
browser: Browser | None = None

@app.on_event("startup")
async def startup_event():
    global browser
    p = await async_playwright().start()
    browser = await p.chromium.launch()

@app.on_event("shutdown")
async def shutdown_event():
    await browser.close()

@app.get("/")
async def read_root():
    return {"Hello": "World"}

@app.get("/playwright")
async def run_playwright():
    if not browser:
        return {"error": "Browser not initialized"}
    page = await browser.new_page()
    await page.goto("http://playwright.dev")
    page_title = await page.title()
    await page.close()
    return {"page_title": page_title}

注意事项 #

• 安装依赖：执行pip install fastapi uvicorn playwright，然后运行playwright install安装所需的浏览器驱动。
• 无头模式：默认情况下Playwright以无头模式启动浏览器，若需要调试可设置launch(headless=False)。
• 部署注意：在服务器环境部署时，需确保有足够权限运行浏览器，若遇到问题可参考Playwright官方文档的部署指南。

参考文档 #

• FastAPI官方中文文档
• Playwright Python官方中文文档

内容的提问来源于stack exchange，提问作者MrGuemez