On Wed, 2007-03-21 at 16:47 -0700, Gerard M wrote: > Hello django community, I have a HUGE problem, and I would like to > know if some of you guys can help me, the problem is: Im accesing a > database and there is a big chance of not finding the item im looking > for, this is the snipplet of code im using and the "solution" that > I've implemented but it doesn't work as it should:
Maybe a better way to think about this is to look at the exception as meaning "I can't do what you asked for" -- that's what exceptions in programming are for ;) And look carefully at the difference between "get" and "filter" -- "get" is meant to return one, and exactly one, object, while "filter" is meant to return a sequence representing all the objects which match the conditions. Looking at it this way, we can consider the two cases: > z=Dic.objects.filter(DB_Word=worfromtext).distinct() This means, roughly, "give me a sequence representing all the distinct things which match these criteria". And Django can do that -- it returns an empty sequence, because there are no distinct things which match the criteria. In effect it says in response, "you asked for a sequence containing all these objects, and there aren't any, so here's a sequence containing nothing". > e = Entry.objects.get(id=3) Here you're saying to Django, "I promise you that there is one, exactly one, and *only* one object which matches these criteria. Go and get it for me." And when it raises the exception, Django is saying "I couldn't do what you asked -- there wasn't an object matching that" (or, sometimes, it will tell you there were multiple objects). If you need to use "filter" and check whether it found anything, this is a better method: >>> z=Dic.objects.filter(DB_Word=worfromtext).distinct() >>> if not z.count(): print 'ERROR!' The "count" method will tell you how many objects match the QuerySet, and testing it as a boolean like this will let you easily distinguish between cases where there are some objects and cases where there are none. -- "Bureaucrat Conrad, you are technically correct -- the best kind of correct." --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com 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 -~----------~----~----~----~------~----~------~--~---
