Using Q object with variable

Question

I'd like to use the django.db.models.Q object in a way that the query term is coming from a variable.

What i'd like to achieve is identical to this:

q = Q(some_field__icontains='sth')
Obj.objects.filter(q)

, but the some_field value should come from a variable:

field_name='some_field'
q = Q('%s__icontains=sth' % field_name)
Obj.objects.filter(q)

, but this solution does not give me the correct result of course.

I also tried to use dictionary this way:

dt = {'%s__icontains' % field_name: 'sth'}
q = Q(**dt)
Obj.objects.filter(q)

, but this also fails on the result.

How could I use the Q object using variables as query term?

Thanks.

Commentative

What do you mean with "fails on the result"? – Audriaaudrie

It does not returns the correct (the expected) number of results. Actually it results 0. – Commentative

Are you sure field_name is the some_field here? If you work with another field_name, of course the result can be different. – Audriaaudrie

Answer 1

You can pass a 2-tuple to a Q object with the name of the fieldname(s) and lookups as first item, and the value as second item:

Obj.objects.filter(Q(('%s__icontains' % field_name, 'sth')))

this is probably the most convenient way. That being said the dictionary unpacking, although less elegant, should also work.

Audriaaudrie

Unfortunately the dictionary way does not work, but your solution does! Thanks. – Commentative

I am surprised that Obj.objects.filter(Q(**dt)) didn't work, but why? 🤔🤔 – Ramakrishna

Unpacking definitely works. Worked for me. – Ameeameer