"Ian Kelly" wrote in message
news:CALwzid=ssdsm8hdan+orj54a_jeu9wc8103iqgkaah8mrj-...@mail.gmail.com...
On Jan 29, 2016 11:04 PM, "Frank Millman" <fr...@chagford.com> wrote:
>
> Hi all
>
> To loop though an iterator one usually uses a higher-level construct
> such
as a 'for' loop. However, if you want to step through it manually you can
do so with next(iter).
>
> I expected the same functionality with the new 'asynchronous iterator'
> in
Python 3.5, but I cannot find it.
>
> I can achieve the desired result by calling 'await aiter.__anext__()',
but this is clunky.
>
> Am I missing something?
async for x in aiter:
pass
Can only be used inside a coroutine, of course.
I know that you can use this to loop through the entire iterator, but I have
a special case.
There are times when I want to execute a SELECT statement, and test for
three possibilities -
- if no rows are returned, the object does not exist
- if one row is returned, the object does exist
- if more that one row is returned, raise an exception
We had a recent discussion about the best way to do this, and ChrisA
suggested the following, which I liked -
cur.execute('SELECT ...)
try:
row = next(cur)
except StopIteration:
# row does not exist
else:
try:
next_row = next(cur)
except StopIteration:
# row does exist
else:
# raise exception
Now that I have gone async, I want to do the same with an asynchronous
iterator.
Frank
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