Simeon Franklin

Blog :: The best way to OR a list of Django ORM Q objects

14 June 2011

A co-worker asked me today about the best way to OR together a list of Q objects in the Django ORM. Usually you have a specific number of conditions and you can use Q objects and the bitwise OR operator to logical OR the query conditions together. The Q object is necessary because multiple arguments or successive calls to .filter are ANDed. But what if you have an arbitrary number of Q conditions?

One suggestion is to use the undocumented .add method of the Q object in a loop to add multiple query conditions together. I thought this might be a good use case for reduce and the operator module:

# Normal Usage with the | operator
from django.db.models import Q
qs = MyModel.objects.filter(Q(cond1=1) | Q(cond2="Y"))

#but given a list of Q conditions
from operator import __or__ as OR
lst = [Q(...), Q(...), Q(...)]
qs = MyModel.objects.filter(reduce(OR, lst))

Is this the most Pythonic approach?

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