How to automatically assign a number to an "Order"?

Question

Django

Good afternoon.
There is a model:

class Order(models.Model):
    '''Заказ'''
    order_number = ???
    date_added = models.DateTimeField(auto_now_add=True)
    date_shipment = models.DateField()

    def __str__(self):
        return self.order_number

Tell me how to automatically assign a unique value to "order_number". It is necessary that at the time of creating the order, the number is immediately assigned and reserved, even if the client does not save the order.

Answer 1

What id does not suit?

Answer 2

Well, for example, do this in the view:

...
next_number = Order.objects.count() + 1
form = OrderForm({'оrder_number': next_number})
...

depending on what your uniqueness should be based on.