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

Primary key attribute usually assigned by the database when the instance saved first time. So you can use something like if instance.pk is None

I am not sure if this is the recommended way but @Radagast’s method didnt work for me(not sure if its because I use custom Pk’s).

I tried the following(not sure if this is the best way):

@receiver(pre_save, sender=YourModelName, weak=False, )
def presave_payment_model_check(sender, instance=None, created=False, **kwargs):
    #Reference: https://stackoverflow.com/questions/11561722/django-what-is-the-role-of-modelstate
    if instance._state.adding:
        # we would need to create the object
        print "Creating an object"
    else:
        #we are updating the object
        print "Updating an object"
    

Reference: Django : What is the role of ModelState?

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.

Using instance._state.adding is the most logical approach, as you will be able to tell the model state exists or is new, regardless whether the primary key as been assigned or not.

When pk is a custom uuid field, instance.pk will also have value on create.

You can try this.

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