How to set a callable function to AutoField default attribute?

Question

I'm trying to overwrite the pk of my models to use a random generator.

Here's the model field:

pk = models.AutoField(auto_created=True, primary_key=True, verbose_name='ID', default=genkey)

and the keygenerator:

def genkey():
    return random.randrange(1,142857)

So, I would like to make the autofield to execute the genkey function as much as possible until it gets a non-used key. Is there an attribute that I didn't find or do I need to code it in the generator (by getting all the used keys) ?

My main goal is to make a generator as generic as possible, not define a custom generator for each model.

Answer 1

After making some research and tests, I ended up creating a class.

class RandomIDKey(models.Model):
    id = models.IntegerField(
        auto_created=True,
        primary_key=True,
        serialize=False,
        verbose_name='ID',
        unique=True,
        db_index=True,
        editable=False
    )

    def save(self, *args, **kwargs):
        if not self.id:
            self.id = genkey(type(self))
        super().save(*args, **kwargs)

    class Meta:
        abstract = True

with a public function:

def genkey(model):
    generated_key = random.randrange(1, 2147483648)
    if model.objects.filter(pk=generated_key).exists():
        generated_key = genkey(model)
    return generated_key

Using an AutoField is a bad idea since the field is not auto-generated by the database, hence the IntegerField