On 10 fev, 12:42, Luc Saffre <luc.saf...@gmx.net> wrote: > Thank you, Henrique, for dropping in. > > Django's current behaviour is not correct because it forces me to access > non-nullable FK fields differently than nullable ones. "In Python, > throwing exceptions for expected outcomes is considered very bad form" > [1]. Django should raise an exception only if I try to save an instance > with invalid data (for example None in a non-nullable FK field), but not > when I try to access any data, may it be valid or not > > Luc
The exception doesn't come from the fact you're accessing an attribute. It comes from the related lookup, Django is just doing the right thing and letting the DoesNotExist exception flow up. It's better if you see things this way. Also, the DoesNotExist exception is far from undocumented. Thru the docs and tutorials you see the idiom on how to handle it quite a few times. [1] It also makes perfect sense to handle nullable FK's different than non- nullable ones. One have a constraint imposed, the other not. Returning None to a non-nullable FK, *this* would be what I call unexpected behaviour. Remember also that this is not a pure OO world. If we were seeing things as just relations between classes, I would agree with you. But we're dealing with a cumbersome thing that is the database, and there's always a mismatch between the ER and OO models. [2] Anyway, there's certainly nothing wrong or strange on throwing exceptions on accessing attributes in Python (or in any dynamic language, I would say), as any attribute on Python can be, in fact, a method (@property). I'm surprised how opposing you feel on this, my feeling is that you come from a different background, working with languages that enforce exception handling in a special way (Java, C#). But it's really getting into the field of personal taste now. [1] http://docs.djangoproject.com/en/1.1/ref/models/querysets/#id5 [2] http://www.sbql.pl/Topics/ImpedanceMismatch.html -- You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to django-develop...@googlegroups.com. To unsubscribe from this group, send email to django-developers+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-developers?hl=en.
