Re: Insert AUTOMATICALLY random string in username field

[Eric Chamberlain]

On Jan 14, 2010, at 6:45 AM, nameless wrote:

> 
> 
> I want username field is automatically filled with this value:
> 
> username = str(n);
> 
> where n is a number of 10 digits ( autoincremented or random ).
> 
> .
> 
> I tried to add this in save method:
> 
> username = str(random.randint(10,99))
> 
> but there is a collision problem when n is the same for 2 users
> ( although rare initially ).
> 
> .
> 
> How do I do this ?
> 

We did something like:

def register_user(email, password, first_name=None, last_name=None, 
agree_to_eula=True):

def generate_username():
"""Generate a random 30-character username. Username can only be 
alphanumeric or underscore."""
return ''.join([choice(string.letters + string.digits + '_') for i in 
range(30)])

email = email.strip()
if not email_re.search(email):
raise InvalidEmailAddressExcept

if len(password.strip()) < 6:
#TODO: pass password length info back to exception, so it's not hard 
coded in two locations
raise InvalidPasswordExcept

try:
user = authenticate_user(email,password,agree_to_eula)
except AuthenticationFailedExcept:
raise AccountExistsAuthenticationFailedExcept
except UserNotFoundExcept:
# we need to create this user
while True:
try:
user = User.objects.create_user(username=generate_username(),
  email=email, password=password)
except IntegrityError:
# this means the username already exists loop and try again 
with a new username
continue
else:
# we successfully created the user, leave the loop
break

if first_name:
user.first_name = first_name
if last_name:
user.last_name = last_name
user.save()
profile = Profile(user=user)
if agree_to_eula:
profile.agree_to_eula()
profile.save()
else:
profile = user.get_profile()

return {'user': user,}

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Re: Insert AUTOMATICALLY random string in username field

[Tom Evans]

On Thu, Jan 14, 2010 at 6:34 PM, nameless  wrote:
> uuid is too long for username field ( max 30 characters ). "n" should
> be a number of 10 digits :)
>
>

Er, a UUID is a 128 bit number. In its standard 'for humans' format it
is represented as 36 character hexadecimal string (ie 288 bits), but
how you pack that into your database is your concern - here is a way
to ensure a 24 character ascii UUID:

>>> import base64
>>> import uuid
>>> print base64.b64encode(uuid.uuid4().bytes)
y1WjDxxOT0KQVe4Jkwuj2g==
>>> print len(base64.b64encode(uuid.uuid4().bytes))
24

although django will still barf on that, it wont accept '/', '=' or
'+' as part of a username - a really pointless and arbitrary
validation rule imo.

Cheers

Tom
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Re: Insert AUTOMATICALLY random string in username field

[Tom Evans]

On Thu, Jan 14, 2010 at 2:45 PM, nameless  wrote:
>
>
> I want username field is automatically filled with this value:
>
> username = str(n);
>
> where n is a number of 10 digits ( autoincremented or random ).
>
> .
>
> I tried to add this in save method:
>
> username = str(random.randint(10,99))
>
> but there is a collision problem when n is the same for 2 users
> ( although rare initially ).
>
> .
>
> How do I do this ?
>
> Thanks ^_^
>

Use a version 4 UUID instead. If you generate 1 billion version 4
UUIDs a second for 100 years, you have ~ 50% chance of a collision.
They are also built in to later versions of python (2.5+):

>>> import uuid
>>> print uuid.uuid4()
92d6a4f4-918d-4a9b-8251-3150c88c62e7


Cheers

Tom
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Re: Insert AUTOMATICALLY random string in username field

[Shawn Milochik]

Do a Google search on 'mysql' and 'sequences.'

Also, have a look at MySQL's last_insert_id() function. Maybe that's  
all you need to use an autonumber as a sequence.


Shawn

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Re: Insert AUTOMATICALLY random string in username field

[nameless]

Sequences are best solution for me but I don't know how to implement
its in django+mysql.
I tought also to use id as username but I don't know how do this :-\

Could you explain me how do pleaseee ?
Thank you


---
On Jan 14, 4:16 pm, Shawn Milochik  wrote:
> There are a bunch of ways you can do it. As a previous poster said, you can 
> take 10 digits of the current timestamp. However, be wary of daylight saving 
> time changes (if you have them on your server), and the possibility of any 
> conflict if you change servers, have a backup server, or ever expand to 
> multiple servers for your application.
>
> A possibility, if you're open to alphanumeric strings, is a uuid, 
> specifically uuid4 or uuid1. Check out the documentation to see if they'd 
> work for you. If you don't care to necessarily limit it to 10 characters, and 
> you don't mind alpha-numeric characters, then just use a uuid4 and you're 
> done.http://docs.python.org/library/uuid.html
>
> Yet another possibility is to use the capability of your database to create 
> sequences. If you're using Postgres, it has a SEQUENCE which you can create, 
> and always ask it for the next one. You can start a sequence at any number 
> you like, in order to get the size you want. We do something similar for 
> generating customer numbers. We have a sequence, and we use it appended to a 
> static set of digits for the particular program the customer is in. So, for 
> example, all customers in program X would have a customer number of 10 digits 
> starting with '1001' and ending with an incremental number. There are ways to 
> do this with other databases. Worst-case you can create a table with an 
> auto-increment key and just use its primary key for your next digit.
>
> One more, but not last nor least, is to have your model generate the string 
> you want by one of the means above, or something completely different, then 
> override the save() of your model to check to ensure that this key doesn't 
> exist already. This is less than ideal, but maybe there's a case to be made 
> for it. Just throwing it in as an option.
>
> Shawn
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Re: Insert AUTOMATICALLY random string in username field

[Shawn Milochik]

There are a bunch of ways you can do it. As a previous poster said, you can 
take 10 digits of the current timestamp. However, be wary of daylight saving 
time changes (if you have them on your server), and the possibility of any 
conflict if you change servers, have a backup server, or ever expand to 
multiple servers for your application.

A possibility, if you're open to alphanumeric strings, is a uuid, specifically 
uuid4 or uuid1. Check out the documentation to see if they'd work for you. If 
you don't care to necessarily limit it to 10 characters, and you don't mind 
alpha-numeric characters, then just use a uuid4 and you're done.
http://docs.python.org/library/uuid.html

Yet another possibility is to use the capability of your database to create 
sequences. If you're using Postgres, it has a SEQUENCE which you can create, 
and always ask it for the next one. You can start a sequence at any number you 
like, in order to get the size you want. We do something similar for generating 
customer numbers. We have a sequence, and we use it appended to a static set of 
digits for the particular program the customer is in. So, for example, all 
customers in program X would have a customer number of 10 digits starting with 
'1001' and ending with an incremental number. There are ways to do this with 
other databases. Worst-case you can create a table with an auto-increment key 
and just use its primary key for your next digit. 

One more, but not last nor least, is to have your model generate the string you 
want by one of the means above, or something completely different, then 
override the save() of your model to check to ensure that this key doesn't 
exist already. This is less than ideal, but maybe there's a case to be made for 
it. Just throwing it in as an option. 

Shawn-- 
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Re: Insert AUTOMATICALLY random string in username field

[Stephen Emslie]

How about a timestamp?

  import time
  name = str(time.time())

On Thu, Jan 14, 2010 at 2:45 PM, nameless  wrote:

>
>
> I want username field is automatically filled with this value:
>
> username = str(n);
>
> where n is a number of 10 digits ( autoincremented or random ).
>
> .
>
> I tried to add this in save method:
>
> username = str(random.randint(10,99))
>
> but there is a collision problem when n is the same for 2 users
> ( although rare initially ).
>
> .
>
> How do I do this ?
>
> Thanks ^_^
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To post to this group, send email to django-us...@googlegroups.com.
> To unsubscribe from this group, send email to
> django-users+unsubscr...@googlegroups.com
> .
> For more options, visit this group at
> http://groups.google.com/group/django-users?hl=en.
>
>
>
>
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