On Mon, Mar 30, 2009 at 6:26 PM, famousactress <[email protected]>wrote:
> > I don't think so.. because I was using .get() first, and found that it > throws an exception if the query returns no results. Isn't that true? > I prefer my exceptions to be, exceptional :) > > Phill > > On Mar 30, 3:07 pm, Dougal Matthews <[email protected]> wrote: > > I think you are looking for get() > > > > facilityList = Facility.objects.get(name = facilityName) > > > > http://docs.djangoproject.com/en/dev/topics/db/queries/#field-lookups > > > > Dougal > > > > --- > > Dougal Matthews - @d0ugalhttp://www.dougalmatthews.com/ > > > > 2009/3/30 famousactress <[email protected]>: > > > > > > > > > Hello folks. I'm new to python, new to Django, but very old to ORMs > > > (via Java's Hibernate, mostly)... > > > > > I naively assumed that QuerySet.filter() would return me None, if > > > there were no results. Instead it returns an empty list. That's not > > > terrible, but for some things, it can make code more cumbersome. > > > Consider the following: > > > > > def ensureFacilityExists(facilityName): > > > > > facilityList = Facility.objects.filter(name = facilityName) > > > > > if len(facilityList) == 1: > > > return facilityList[0] > > > elif len(facilityList == 0: > > > facility = Facility(name = facilityName) > > > facility.save() > > > return facility > > > else: > > > raise Exception("More than one facility with that name!") > > > > > This is a bit clunky for this case. I looked for a method on QuerySet > > > that would clean this up, but didn't find one. I may have missed > > > something. Here's what I did to clean my case up though: > > > > > def ensureFacilityExists(facilityName): > > > > > facility = Facility.objects.filter(name = facilityName).only() > > > > > if facility == None: > > > facility = Facility(name = facilityName) > > > facility.save() > > > > > return facility > > > > > ... In order to do this, I added the only() method to QuerySet: > > > > > def queryset_only(self): > > > i = len(self) > > > if i == 0: > > > return None > > > elif i > 1: > > > raise Exception("More than one element in this querySet!!") > > > else: > > > return self[0] > > > > > import new > > > from django.db.models.query import QuerySet > > > QuerySet.only = new.instancemethod(queryset_only,None,QuerySet) > > > > > My question is: > > > > > Is there another facility for doing this already built into Django's > > > ORM? If not, is this a change that seems valuable to anyone else? > > > > > Thanks, > > > Phill > > > What's wrong with the code: try: obj = Model.objects.get(param=val) except Model.DoesNotExist: obj = None Alex -- "I disapprove of what you say, but I will defend to the death your right to say it." --Voltaire "The people's good is the highest law."--Cicero --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
