本文共 7315 字，大约阅读时间需要 24 分钟。

代码有点多，我都注释过了，该文章仅协程部分，python官网入门教程的化请看我github:

"""作者：杨涵x时间：2021/4/30"""# import asyncio# async def main():#     print('Hello ...')#     await asyncio.sleep(1)#     print('... World!')# asyncio.run(main())'''等待 1 秒后打印 "hello"，然后 再次 等待 2 秒后打印 "world"'''# import asyncio# import time## async def say_after(delay, what):#     await asyncio.sleep(delay)#     print(what)# async def main():#     print(f"started at {time.strftime('%X')}")#     await say_after(1, 'hello')#     await say_after(2, 'world')#     print(f"finished at {time.strftime('%X')}")# asyncio.run(main())'''asyncio.create_task() 函数用来并发运行作为 asyncio 任务 的多个协程。'''# async def main():#     task1 = asyncio.create_task(#         say_after(1, 'hello'))#     task2 = asyncio.create_task(#         say_after(2, 'world'))#     print(f"started at {time.strftime('%X')}")#     # Wait until both tasks are completed (should take#     # around 2 seconds.)#     await task1#     await task2##     print(f"finished at {time.strftime('%X')}")# asyncio.run(main())'''Python 协程属于 可等待 对象，因此可以在其他协程中被等待'''# import asyncio## async def nested():#     return 42## async def main():#     # Nothing happens if we just call "nested()".#     # A coroutine object is created but not awaited,#     # so it *won't run at all*.#     # Let's do it differently now and await it:#     print(await nested())  # will print "42".## asyncio.run(main())'''协程函数: 定义形式为 async def 的函数;协程对象: 调用 协程函数 所返回的对象。''''''当一个协程通过 asyncio.create_task() 等函数被封装为一个 任务，该协程会被自动调度执行'''# import asyncio## async def nested():#     return 42## async def main():#     # Schedule nested() to run soon concurrently#     # with "main()".#     task = asyncio.create_task(nested())##     # "task" can now be used to cancel "nested()", or#     # can simply be awaited to wait until it is complete:#     await task# asyncio.run(main())'''运行 asyncio 程序''''''asyncio.run(coro, *, debug=False)¶'''# import asyncio# async def main():#     await asyncio.sleep(1)#     print('hello')## asyncio.run(main())'''创建任务''''''asyncio.create_task(coro, *, name=None)¶'''# import asyncio# async def coro():#     return 2021# task = asyncio.create_task(coro())#python3.7+# This works in all Python versions but is less readable# task = asyncio.ensure_future(coro())#before python3.7'''休眠'''''' asyncio.sleep(delay, result=None, *, loop=None)¶''''''以下协程示例运行 5 秒，每秒显示一次当前日期'''# import asyncio# import datetime## async def display_date():#     loop = asyncio.get_running_loop()#     end_time = loop.time() + 5.0#     while True:#         print(datetime.datetime.now())#         if (loop.time() + 1.0) >= end_time:#             break#         await asyncio.sleep(1)## asyncio.run(display_date())'''并发运行任务'''''' asyncio.gather(*aws, loop=None, return_exceptions=False)¶'''# import asyncio## async def factorial(name, number):#     f = 1#     for i in range(2, number + 1):#         print(f"Task {name}: Compute factorial({i})...")#         await asyncio.sleep(1)#         f *= i#     print(f"Task {name}: factorial({number}) = {f}")## async def main():#     # Schedule three calls *concurrently*:#     await asyncio.gather(#         factorial("A", 2),#         factorial("B", 3),#         factorial("C", 4),#     )## asyncio.run(main())'''屏蔽取消操作''''''asyncio.shield(aw, *, loop=None)保护一个 可等待对象 防止其被 取消'''# res = await shield(something())#demo'''如果希望完全忽略取消操作 (不推荐) 则 shield() 函数需要配合一个 try/except 代码段'''# try:#     res = await shield(something())# except CancelledError:#     res = None'''超时''''''asyncio.wait_for(aw, timeout, *, loop=None)¶'''# import asyncio# async def eternity():#     # Sleep for one hour#     await asyncio.sleep(3600)#     print('yay!')## async def main():#     # Wait for at most 1 second#     try:#         await asyncio.wait_for(eternity(), timeout=1.0)#     except asyncio.TimeoutError:#         print('timeout!')## asyncio.run(main())'''简单等待''''''syncio.wait(aws, *, loop=None, timeout=None, return_when=ALL_COMPLETED)'''# 用法:# import asyncio# done, pending = await asyncio.wait(aws)# async def foo():#     return 42## task = asyncio.create_task(foo())# done, pending = await asyncio.wait({task})## if task in done:#     asyncio.run(task)#     # Everything will work as expected now.'''在线程中运行''''''asyncio.to_thread(func, /, *args, **kwargs)在不同的线程中异步地运行函数 func。''''''这个协程函数主要是用于执行在其他情况下会阻塞事件循环的 IO 密集型函数/方法'''# import asyncio,time# def blocking_io():#     print(f"start blocking_io at {time.strftime('%X')}")#     # Note that time.sleep() can be replaced with any blocking#     # IO-bound operation, such as file operations.#     time.sleep(1)#     print(f"blocking_io complete at {time.strftime('%X')}")## async def main():#     print(f"started main at {time.strftime('%X')}")##     await asyncio.gather(#         asyncio.to_thread(blocking_io),#         asyncio.sleep(1))#     print(f"finished main at {time.strftime('%X')}")# asyncio.run(main())''':要取消一个正在运行的 Task 对象可使用 cancel() 方法。调用此方法将使该 Task 对象抛出一个 CancelledError 异常给打包的协程''''''以下示例演示了协程是如何侦听取消请求的'''# import asyncio# async def cancel_me():#     print('cancel_me(): before sleep')##     try:#         # Wait for 1 hour#         await asyncio.sleep(3600)#     except asyncio.CancelledError:#         print('cancel_me(): cancel sleep')#         raise#     finally:#         print('cancel_me(): after sleep')## async def main():#     # Create a "cancel_me" Task#     task = asyncio.create_task(cancel_me())##     # Wait for 1 second#     await asyncio.sleep(1)##     task.cancel()#     try:#         await task#     except asyncio.CancelledError:#         print("main(): cancel_me is cancelled now")## asyncio.run(main())'''基于生成器的协程''''''@asyncio.coroutine用来标记基于生成器的协程的装饰器。此装饰器使得旧式的基于生成器的协程能与 async/await 代码相兼容'''# import asyncio# @asyncio.coroutine# def old_style_coroutine():#     yield from asyncio.sleep(1)## async def main():#     await old_style_coroutine()'''队列能被用于多个的并发任务的工作量分配：'''import asyncioimport randomimport timeasync def worker(name, queue):    while True:        # Get a "work item" out of the queue.        sleep_for = await queue.get()        # Sleep for the "sleep_for" seconds.        await asyncio.sleep(sleep_for)        # Notify the queue that the "work item" has been processed.        queue.task_done()        print(f'{name} has slept for {sleep_for:.2f} seconds')async def main():    # Create a queue that we will use to store our "workload".    queue = asyncio.Queue()    # Generate random timings and put them into the queue.    total_sleep_time = 0    for _ in range(20):        sleep_for = random.uniform(0.05, 1.0)        total_sleep_time += sleep_for        queue.put_nowait(sleep_for)    # Create three worker tasks to process the queue concurrently.    tasks = []    for i in range(3):        task = asyncio.create_task(worker(f'worker-{i}', queue))        tasks.append(task)    # Wait until the queue is fully processed.    started_at = time.monotonic()    await queue.join()    total_slept_for = time.monotonic() - started_at    # Cancel our worker tasks.    for task in tasks:        task.cancel()    # Wait until all worker tasks are cancelled.    await asyncio.gather(*tasks, return_exceptions=True)    print('====')    print(f'3 workers slept in parallel for {total_slept_for:.2f} seconds')    print(f'total expected sleep time: {total_sleep_time:.2f} seconds')asyncio.run(main())

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