Question

I want username field is automatically filled with this value:

username = str(n);

where n is a number (autoincremented or random).

I tried to add this in save method:

username = str(random.randint(0,1000000)

but there is a collision problem when n is the same for 2 users.

How do I do this ?

Answer 1

Generate it
username = str(random.randint(0,1000000)
and check for a user with such a name
User.objects.get(username=username)
if you find someone, generate a new one.

def GenerateUsername():
    username = str(random.randint(0,1000000))

    try:
        User.objects.get(username=username)
        return GenerateUsername()
    except User.DoesNotExist:
        return username;