django post_save signals on update

update() is converted directly to an SQL statement; it doesn't call save() on the model instances, and so the pre_save and post_save signals aren't emitted. If you want your signal receivers to be called, you should loop over the queryset, and for each model instance, make your changes and call save() yourself.

Just one more thing to @Ismali Badawi's answer.

---

This calls post_save

user = User.objects.get(id=1) 
user.username='edited_username' 
user.save()

This does not call post_save

User.objects.filter(id=1).update(username='edited_username')

---

In the code,

from django.db.models.signals import post_save

@receiver(post_save, sender=User)
def do_something_when_user_updated(sender, instance, created, **kwargs):
    if not created:
        # User object updated
        user_obj = instance
        pass