Django Custom Queryset filters

Question

Is there, in Django, a standard way to write complex, custom filters for QuerySets?

Just as I can write

MyClass.objects.all().filter(field=val)

I'd like to do something like this :

MyClass.objects.all().filter(customFilter)

I could use a generator expression

(x for x in MyClass.objects.all() if customFilter(x))

but that would lose the chainability and whatever other functions the QuerySets provide.

Speculator

Answer 1

I think you may need custom managers.

Ecosphere

I guess I do need this. But it looks awfully complicated compared to just being able to pass a filter function in on the fly. – Speculator

It's not very complicated, and it's a good practice to make custom managers, especially if you plan on caching stuff from db etc. – Ecosphere

Answer 2

The recommendation to start using manager methods is a good one, but to answer your question more directly: yes, use Q objects. For example:

from django.db.models import Q

complexQuery = Q(name__startswith='Xa') | ~Q(birthdate__year=2000)

MyModel.objects.filter(complexQuery)

Q objects can be combined with | (OR), & (AND), and ~ (NOT).

Bernadinebernadotte