为什么我在 Python asyncio 中收到 "Task was destroyed but it is pending" 错误？

Question

我用asyncio又漂亮aiohttp。主要思想是我向服务器发出请求（它是 returns 链接），然后我想从 parallel 中的所有链接下载文件（类似于 example).

代码：

import aiohttp
import asyncio

@asyncio.coroutine
def downloader(file):
    print('Download', file['title'])
    yield from asyncio.sleep(1.0) # some actions to download
    print('OK', file['title'])


def run():
    r = yield from aiohttp.request('get', 'my_url.com', True))
    raw = yield from r.json()
    tasks = []
    for file in raw['files']:
        tasks.append(asyncio.async(downloader(file)))
        asyncio.wait(tasks)

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(run())

但是，当我尝试运行它时，我有很多 "Download ..." 输出和

Task was destroyed but it is pending!

'OK + filename'.

什么都没有

我该如何解决？

Answer 1

您忘记 yield from 呼叫 asyncio.wait。您的缩进也可能有误；在遍历整个 raw['files'] 列表后，您只想运行它。这是修复了两个错误的完整示例：

import aiohttp
import asyncio

@asyncio.coroutine
def downloader(file):
    print('Download', file['title'])
    yield from asyncio.sleep(1.0) # some actions to download
    print('OK', file['title'])

@asyncio.coroutine
def run():
    r = yield from aiohttp.request('get', 'my_url.com', True))
    raw = yield from r.json()
    tasks = []
    for file in raw['files']:
        tasks.append(asyncio.async(downloader(file)))
    yield from asyncio.wait(tasks)

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(run())

如果不调用 yield from，run 会在您遍历整个文件列表后立即退出，这意味着您的脚本会退出，导致一大堆未完成的 downloader 待销毁的任务，并显示您看到的警告。

为什么我在 Python asyncio 中收到 "Task was destroyed but it is pending" 错误？

Why am I getting a "Task was destroyed but it is pending" error in Python asyncio?

python

python-asyncio

aiohttp