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

python django keyword-argument
Heyl1 picture Heyl1 · Aug 31, 2010 · Viewed 18.3k times · Source

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.

Answer

Radagast picture Radagast · Aug 26, 2012

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

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