On Jun 17, 2013, at 5:33 AM, Wichert Akkerman <wich...@wiggy.net> wrote:
>
> On Jun 17, 2013, at 08:58 , Chris Withers <ch...@simplistix.co.uk> wrote:
>
>> Hi All,
>>
>> I seems to commonly need to do a query which should return zero or one
>> mapped objects.
>>
>> .one() isn't what I want as no returned object is ok.
>>
>> .first() isn't what I want as if my query would return more than one object,
>> I have the query wrong and so want an exception.
>>
>> Is there something already available that meets this need?
>
> This will requrie you to run a query which limits the result to max 2 rows so
> you can check if more than one result would be returned. I would just create
> a simple wrapper function:
>
>
> def one_optional(query):
> rows = query.limit(2).all()
> count = len(rows)
> if count == 0:
> return None
> elif count == 1:
> return rows[0]
> else:
> raise RuntimeError('More than one result found.')
you could even drop the limit(2) so that the query renders more simply if
eagerloads are present.
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