Python进阶教程：异步编程（asyncio）

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import asyncio
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async def hello():
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    print("开始执行")
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    await asyncio.sleep(1)  # 模拟异步等待
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    print("执行完成")
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# 运行协程
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asyncio.run(hello())

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import asyncio
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import time
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async def fetch(name, delay):
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    print(f"{name} 开始请求...")
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    await asyncio.sleep(delay)
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    print(f"{name} 完成！")
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    return f"{name}的数据"
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async def main():
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    start = time.perf_counter()
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    # 并发执行多个协程
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    results = await asyncio.gather(
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        fetch("请求A", 2),
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        fetch("请求B", 1),
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        fetch("请求C", 3),
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    )
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    print(results)
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    print(f"总耗时：{time.perf_counter() - start:.1f}s")  # 约 3s 而非 6s
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asyncio.run(main())

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import asyncio
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async def worker(name, delay):
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    await asyncio.sleep(delay)
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    return f"{name} 完成"
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async def main():
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    # 创建任务（不立即 await，让它们并行）
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    task1 = asyncio.create_task(worker("任务1", 2))
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    task2 = asyncio.create_task(worker("任务2", 1))
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    # 等待所有任务
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    results = await asyncio.gather(task1, task2)
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    print(results)
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asyncio.run(main())

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# pip install aiohttp
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import asyncio
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import aiohttp
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import time
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async def fetch_url(session, url):
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    async with session.get(url) as resp:
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        return await resp.text()
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async def main():
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    urls = ["https://httpbin.org/get"] * 5
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    async with aiohttp.ClientSession() as session:
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        start = time.perf_counter()
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        # 并发请求
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        responses = await asyncio.gather(
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            *(fetch_url(session, url) for url in urls)
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        )
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        print(f"完成 {len(responses)} 个请求，耗时 {time.perf_counter()-start:.2f}s")
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asyncio.run(main())

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import asyncio
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import time
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def sync_blocking():
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    """模拟阻塞操作（如 CPU 计算、旧库调用）"""
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    time.sleep(2)
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    return "同步结果"
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async def main():
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    print("开始")
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    # 用 run_in_executor 把阻塞操作丢到线程池
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    loop = asyncio.get_running_loop()
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    result = await loop.run_in_executor(None, sync_blocking)
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    print(result)
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asyncio.run(main())

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import asyncio
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async def slow_task():
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    await asyncio.sleep(10)
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    return "终于完成了"
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async def main():
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    try:
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        # 3 秒超时
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        result = await asyncio.wait_for(slow_task(), timeout=3)
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        print(result)
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    except asyncio.TimeoutError:
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        print("任务超时，已取消")
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asyncio.run(main())  # 任务超时，已取消

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import asyncio
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import aiohttp
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import time
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async def download(session, index):
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    """模拟异步下载文件"""
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    await asyncio.sleep(index * 0.3)
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    return f"文件{index} 下载完成"
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async def main():
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    async with aiohttp.ClientSession() as session:
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        start = time.perf_counter()
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        tasks = [download(session, i) for i in range(1, 8)]
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        results = await asyncio.gather(*tasks)
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        for r in results:
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            print(r)
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        print(f"总耗时：{time.perf_counter()-start:.2f}s")
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asyncio.run(main())