[Django]-Django getting foreign-key object list

B.objects.filter(a__in=a_list)

note that you can filter on related objects like this (instead if executing two queries do it in one)

for example if your a_list is a query like this:

a_list = A.objects.filter(field=2)

you can filter B like this:

B.objects.filter(a__field=2)

which is more readable and also django can optimize it too)

Update: you can query reversed relations the same way

A.objects.filter(b__in=b_list)
A.objects.filter(b__field=2)

note that it’s better to change your code to

a = model.ForeignKey(A, related_name='b')

b is the name of the field in reveres relations so an_a_instance.b.all() returns all instances of b which are pointing at given a_instance