與事件循環(huán)進(jìn)行交互，最基本的方式就是任務(wù)，任務(wù)封裝了協(xié)程和自動(dòng)跟蹤它的狀態(tài)。任務(wù)是Future類的子類，所以其它協(xié)程可以等待任務(wù)完成，或當(dāng)這些任務(wù)完成獲取返回結(jié)果。

在這里通過create_task()函數(shù)來創(chuàng)建一個(gè)任務(wù)實(shí)例，然后事件循環(huán)就運(yùn)行這個(gè)任務(wù)，直到這個(gè)任務(wù)返回為止：

import asyncio async def task_func(): print(’in task_func’) return ’the result’ async def main(loop): print(’creating task’) task = loop.create_task(task_func()) print(’waiting for {!r}’.format(task)) return_value = await task print(’task completed {!r}’.format(task)) print(’return value: {!r}’.format(return_value)) event_loop = asyncio.get_event_loop()try: event_loop.run_until_complete(main(event_loop))finally: event_loop.close()

結(jié)果輸出如下：

creating taskwaiting for <Task pending coro=<task_func() running at D:workcsdnpython_Game1exampleasyncio_create_task.py:4>>in task_functask completed <Task finished coro=<task_func() done, defined at D:workcsdnpython_Game1exampleasyncio_create_task.py:4> result=’the result’>return value: ’the result’

補(bǔ)充知識(shí)：python里創(chuàng)建任務(wù)執(zhí)行一半時(shí)取消任務(wù)執(zhí)行

下例子來演示創(chuàng)建任務(wù)執(zhí)行一半時(shí)取消任務(wù)執(zhí)行，這時(shí)會(huì)拋出異常CancelledError，同時(shí)也提供了一個(gè)機(jī)會(huì)來刪除占用資源等等：

import asyncio async def task_func(): print(’in task_func, sleeping’) try: await asyncio.sleep(1) except asyncio.CancelledError: print(’task_func was canceled’) raise return ’the result’ def task_canceller(t): print(’in task_canceller’) t.cancel() print(’canceled the task’) async def main(loop): print(’creating task’) task = loop.create_task(task_func()) loop.call_soon(task_canceller, task) try: await task except asyncio.CancelledError: print(’main() also sees task as canceled’) event_loop = asyncio.get_event_loop()try: event_loop.run_until_complete(main(event_loop))finally: event_loop.close()

結(jié)果輸出如下：

creating taskin task_func, sleepingin task_cancellercanceled the tasktask_func was canceledmain() also sees task as canceled

以上這篇在python里創(chuàng)建一個(gè)任務(wù)(Task)實(shí)例就是小編分享給大家的全部?jī)?nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持好吧啦網(wǎng)。