python–asyncio.as_completed是否会产生期货或协同程序？_python

概述来自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

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))FalseFalseFalse

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`]

最佳答案What I would like to be able to do is something like this […]
也许不那么方便,但您应该能够使用以下代码提取异常：
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):            try:                res = await future            except Exception as e:                res = e            # ...            # [Do something with `res`]
This [yIElding coroutines rather than futures] seems to defeat the description of .as_completed(). How is the coroutine “completed” if I need to await it?
不是.首次实现asyncio.as_completed时,异步迭代器不存在.没有异步迭代就没有办法在它们完成时返回期货,所以as_completed类型通过屈服(立即)虚拟等待来伪造它,人们必须等待获得实际结果.
即使as_completed产生了实际的期货,也不会对你的用例有所帮助,因为如果没有等待他们的人,这些期货就无法完成.为了提供as_completed让步完成的期货的预期语义,as_completed需要实现异步迭代,其等价的__next__可以等待.
as_completed的惊人行为之前已经提出,我已经通过提供异步迭代提交了an issue来修复它.一旦实现,您的原始代码将只用于更改为async for.          总结       
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python–asyncio.as_completed是否会产生期货或协同程序？

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