Django pre_save signal: check if instance is created not updated, does kwargs['created'] (still) exist?

user_368102 0
Viewed 22876

I am using Django's pre_save signal to implement auto_now_add. There is a lot of discussion on the internet on why you should or shouldn't implement it yourself. I do not appreciate comments on this. Neither on whether I should be rewriting the save function (I have a lot of models that use auto_now_add so using signals makes sense).

My question is:
I would like to check if the instance is created or updated. According to some sources on the internet this can be done by testing if kwargs['created'] is True. However 'created' does not appear in my kwargs even though the instance is newly created. I was just wondering if it has ever existed or that it has disappeared magically. I know I could also test if kwargs['instance'].id is set (this in fact works for me), but I'd like to know if kwargs['created'] still exists.

keyword-argument django python
6 Answers

You can easily check if an instance is created or updated in pre_save in this way:

@receiver(pre_save, sender=MyModel)
def pre_save_user(sender, instance, **kwargs): 
    if instance._state.adding:
        print ('Instance created!')
    else:
        print ('Instance updated!')

Tested with Django 3.0.

user_37504630

You can try this.

@receiver(pre_save, sender=User)
def user(instance, *args, **kwargs):
    if instance.id != None:
user_104953000
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