obj = MyModel.objects.create(val=1)
MyModel.objects.filter(pk=obj.pk).update(val=F('val') + 1)
# At this point obj.val is still 1, but the value in the database
# was updated to 2. The object's updated value needs to be reloaded
# from the database.

#  approach 1)
obj = MyModel.objects.get(pk=obj.pk)

#  approach 2)
obj.refresh_from_db()