"Chris Angelico" wrote in message
news:CAPTjJmoAmVNTCKq7QYaDRNQ67Gcg9TxSXYXCrY==s9djjna...@mail.gmail.com...
On Sat, Jan 30, 2016 at 7:22 PM, Frank Millman <fr...@chagford.com> wrote:
> 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.
Here's a crazy option. (Assuming that a row can't be None. If not, use
a unique sentinel object.)
cur.execute(whatever)
have_row = None
async for row in cur:
if have_row is not None:
raise TooManyRows
have_row = row
if have_row is None:
raise NoRowFound
Not so crazy :-) If Ian doesn’t come up with a better idea I will run with
it.
Here is a slight variation - just variable name changes really, but I think
it is slightly easier to read -
found = False
async for row in cur:
if found:
raise TooManyRows
found = True
if found:
process row
else:
no rows found
Frank
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