python初始异步编程第三节
""" 刚刚我们讲了asyncio 处理请求和异步处理 但是在真实项目开发中，我们往往不会直接使用asyncio来处理网络请求， 而是使用其他封装的类库,例如 aiohttp,aiofile 我们接着前两个案例来完成真实 网络请求抓取数据 和读取数据文件的案例 """ import asyncio import aiohttp import aiofiles from time import perf_counter """ 抓取网页内容异步函数 async: 表示这是一个异步函数 def 定义函数关键字 with 语句会自动管理资源的生命周期，确保即使发生异常也能正确释放资源。它通常与支持上下文管理协议的对象一起使用（这些对象实现了 __enter__() 和 __exit__() 方法）。 with 语法 with open('example.txt', 'r') as file: 这里 as file 是把返回值赋值给file async with用于异步上下文管理， 它确保在操作完成后正确释放资源（例如关闭网络连接）。 aiohttp.ClientSession(): 创建一个 ClientSession 对象，用于管理 HTTP 请求的生命周期。它是 aiohttp 提供的一个类，能够高效复用连接 as session: 将创建的 ClientSession 对象赋值给变量 session，以便后续使用 session.get(url): 使用 session 发起一个 GET 请求到指定的 url as resp: 将返回的响应对象赋值给变量 resp await: 用于等待异步操作完成。在这里，resp.text() 是一个异步方法，它会解析响应内容并返回字符串形式的数据 resp.text(): 调用响应对象的 text() 方法，将响应体以字符串形式返回 """ async def fetch_url(url): async with aiohttp.ClientSession() as session: async with session.get(url) as resp: return await resp.text() async def read_file(file_path): async with aiofiles.open(file_path, 'r') as file: return await file.read() async def main(): url="https://i.cnblogs.com/articles/edit-done;postId=18786562;isPublished=true" file_path="./异步编程第三节测试文件.txt" #把协程请求函数包装成任务 task1=asyncio.create_task(fetch_url(url)) #把协程读取文件函数包装成任务 task2=asyncio.create_task(read_file(file_path)) #获取到携程函数的返回值，使用await url_content=await task1 file_content=await task2 print(url_content) print(file_content) if __name__ == '__main__': #记录开始时间 start_time=perf_counter() #创建事件循环，把协程放入事件循环中 asyncio.run(main()) end_time=perf_counter() print("执行时间：",end_time-start_time)
输出 执行时间： 0.5933730830000001
输出结果：
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