Hello Jason, I don't think this is explicitly documented but I feel like the TypeError raised explicitly states that this isn't supported:
__init__() takes either a Q object or lookups as keyword arguments > Did you end up in this situation by following along the documentation or trial and error? Best, Simon Le jeudi 21 septembre 2017 10:13:11 UTC-4, Jason a écrit : > > I have a model in which I was trying to get a count for records that > matched three variable values and found an interesting edge case not in the > documents > for conditional expressions > <https://docs.djangoproject.com/en/1.11/ref/models/conditional-expressions/#when>. > > Specifically, if you have to use a Q expression for a not query, you can't > mix them with lookups. > > This is all on Django 1.8 with python 2.7.12 > > for example, > > SomeModel.objects.aggregate(total = Count(Case(When(~Q(some_field__icontains > = 'value'), field_two = 2, field_three = True, then = 1), output_field = > IntegerField())) > > will result in a TypeError > > /home/jason/.virtualenvs/work/lib/python2.7/site-packages/django/db/models/expressions.pyc > > in __init__(self, condition, then, **lookups) > 687 condition, lookups = Q(**lookups), None > 688 if condition is None or not isinstance(condition, Q) or > lookups: > --> 689 raise TypeError("__init__() takes either a Q object or > lookups as keyword arguments") > 690 super(When, self).__init__(output_field=None) > 691 self.condition = condition > > TypeError: __init__() takes either a Q object or lookups as keyword > arguments > > However, moving the original to a full ANDed Q expression like > > query = ~Q(some_field__icontains = 'value') & Q(field_two = 2) & > Q(field_three > = True) > SomeModel.objects.aggregate(total = Count(Case(When(query, then = 1), > output_field = IntegerField())) > > works fine. I couldn't find anything specifically about this in the docs, > so is this explicit behavior or an undocumented issue? > -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscr...@googlegroups.com. To post to this group, send email to django-users@googlegroups.com. Visit this group at https://groups.google.com/group/django-users. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/a01a497c-d011-4916-b30f-d00aae20c3e1%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
