django - creating users making their fullname unique

Question

i need small help in the logic of creating user making his name unique:

i have a django user profile. i am creating users in this way:

fullname = request.POST.get('fullname')
random_username = ''.join(random.sample(string.ascii_lowercase, 8))
new_user = User.objects.create_user(random_username, email, passwort)
##update siteprofile of this new user
userprofile = new_user.get_profile()

""" 
    i need to make this fullname unique with this logic:
    for example john is the fullname of new user. i need to check if there are 
    other johns in db, if there is another user with this name, i will name the
    user with 'john1'. if there are 2, the new user will get the name 'john3'
    how can I check this in db in some efficient way?

"""
userprofile.name = fullname
userprofile.save()

Answer 1

You want to check for the IntegrityError on save and update accordingly. Doing a query to check for the names existence creates a race condition where you can search then two separate threads try to create the same fullname at the same time.

from django.db import transaction

@transaction.commit_manually
def set_fullname(userprofile, fullname, i=0):
    new_fullname = u"{}{}".format(fullname, str(i) if i else '')
    try:
        userprofile.fullname = new_fullname
        userprofile.save()

        transaction.commit()

        return userprofile
    except IntegrityError:
        transaction.rollback()

        i += 1
        # Just recursively try until we a valid name. This could be problematic if you
        # have a TON of users, but in that case you could just the filter before then to see
        # what number to start from.
        return set_fullname(userprofile, fullname, i)

userprofile = set_fullname(userprofile, fullname)

Answer 2

For this purpose it would be better to use form https://docs.djangoproject.com/en/dev/topics/forms/ . But if you won't to use forms, you can do it that way:

i = 0
orig_fullname = fullname
created = False
while not created:
    profile, created = UserProfile.objects.get_or_create(name=fullname)
    if not created:
        i+=1
        fullname = orig_fullname + str(i)
# there you have new user's profile

Note, that field 'name' in UserProfile model must have unique=True parameter https://docs.djangoproject.com/en/dev/ref/models/fields/#unique