来自asyncio docs：

asyncio.as_completed(aws,*,loop=None,timeout=None)

Run awaitable objects in the aws set concurrently. Return an iterator

of Future objects. Each Future object returned represents the earliest

result from the set of the remaining awaitables.

我假设这些Future对象中的每一个都具有asyncio.Future中描述的方法：.cancelled(),. exception()和.result().但似乎所产生的元素只是协程,而不是Future对象.我错过了什么？

这似乎打败了.as_completed()的描述.如果我需要等待它,协程如何“完成”？

>>> import asyncio

>>> import aiohttp

>>>

>>> async def get(session,url):

... async with session.request('GET',url) as resp:

... t = await resp.text()

... return t

...

>>> async def bulk_as_completed(urls):

... async with aiohttp.ClientSession() as session:

... aws = [get(session,url) for url in urls]

... for future in asyncio.as_completed(aws):

... for i in ('cancelled','exception','result'):

... print(hasattr(future,i))

... print(type(future))

... try:

... result = await future

... except:

... pass

... else:

... print(type(result))

... print()

...

>>>

>>> urls = (

... 'https://docs.python.org/3/library/asyncio-task.html',... 'https://docs.python.org/3/library/select.html',... 'https://docs.python.org/3/library/this-page-will-404.html',... )

>>>

>>> asyncio.run(bulk_as_completed(urls))

False

False

False

最终,我关心这个的原因是因为我想让异常像asyncio.gather(…,return_exceptions = True)那样冒泡.考虑在调用session.request()时添加一个伪造的URL：

urls = (

'https://docs.python.org/3/library/asyncio-task.html','https://docs.python.org/3/library/select.html','https://docs.python.org/3/library/this-page-will-404.html',# This URL will raise on session.request(). How can I propagate

# that exception to the iterator of results?

'https://asdfasdfasdf-does-not-exist-asdfasdfasdf.com'

)

我希望能够做的是这样的事情(使用Future对象的方法,但这些都不是Future对象,这就是问题)：

async def bulk_as_completed(urls):

async with aiohttp.ClientSession() as session:

aws = [get(session,url) for url in urls]

for future in asyncio.as_completed(aws):

if future.cancelled():

res = futures.CancelledError()

else:

exc = future.exception()

if exc is not None:

res = exc

else:

res = future.result()

# ...

# [Do something with `res`]