Simply handling NoResultFound should work just fine...
def zero_or_one(query):
try:
return query.one()
except NoResultFound:
return None
On Mon, Jun 17, 2013 at 6:36 PM, Michael Bayer <mike...@zzzcomputing.com> wrote:
>
> 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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