async enumeration - possible?

[Frank Millman]

"Frank Millman"  wrote in message news:o1k355$da5$1 at blaine.gmane.org...
>
> Hi all
>
> Python 3.6 has introduced Asynchronous Generators, which work very well.
>
[...]
>
> However, it does not allow you to enumerate over the generator output -
>
[...]
>
> Is there any technical reason for this, or is it just that no-one has got 
> around to writing an asynchronous version yet?

Thanks for the replies.

@Ian
Thanks for your explanation and example.
The example is perfect for my simple requirement.

@Terry
I should have googled for aenumerate - didn't think of it.

However, this recipe is based on Python 3.5 and earlier.
Asynchronous Generators, introduced in 3.6, make it much easier.
See PEP 525 for the details -
    https://www.python.org/dev/peps/pep-0525/

@Chris
I agree, there is a big difference between functions which consume the 
entire iterable before returning the result, and those which behave 
asynchronously and return the value on-the-fly.

I happened upon enumerate. You mentioned zip and map, which are also likely 
to be useful in the right circumstances.

I did not quite follow your example, as I get the opposite result -

Python 3.6.0b4 (default, Nov 22 2016, 05:30:12) [MSC v.1900 64 bit (AMD64)] 
on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import asyncio
>>> loop = asyncio.get_event_loop()

>>> async def gen(n):
...   for i in range(n):
...     yield i
...
>>> async def main():
...   print([x async for x in gen(5)])
...
>>> loop.run_until_complete(main())
[0, 1, 2, 3, 4]

>>> async def main():
...   print(list(x async for x in gen(5)))
...
>>> loop.run_until_complete(main())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File 
"C:\Users\User\AppData\Local\Programs\Python\Python36\lib\asyncio\base_events.py", 
line 466, in run_until_complete
    return future.result()
TypeError: 'async_generator' object is not iterable
>>>

Frank