Django: Generate unique 8 character alphanumeric ID string on form submission

Question

Could someone please help me create a field in my model that generates a unique 8 character alphanumeric string (i.e. A#######) ID every time a user makes a form submission?

My models.py form is currently as follows:

from django.db import models
from django.contrib.auth.models import User

    class Transfer(models.Model):
        id = models.AutoField(primary_key=True)
        user = models.ForeignKey(User)
        timestamp = models.DateTimeField(auto_now_add=True, auto_now=False)

I have looked at pythons UUID feature but these identifiers are quite long and messy compared with what I am looking to generate.

Any help would be hugely appreciated!

How would you prefer uniqueness to be enforced? What sort of collision risks are there? — Christofer Ohlsson, Feb 01 '16 at 09:57

score 0 · Answer 1 · answered Feb 01 '16 at 09:57

0

Something like this:

''.join(random.choice(string.ascii_uppercase) for _ in range(8))

answered Feb 01 '16 at 09:57

egorikem

1,077
11
18

How is the op expected to use this in their field? – Sayse Feb 01 '16 at 10:31
This looks very similar to the answer from [this question](http://stackoverflow.com/questions/2257441/random-string-generation-with-upper-case-letters-and-digits-in-python) also.. – Sayse Feb 01 '16 at 10:39
@ChristoferOhlsson Because the op don't want to use digits – egorikem Feb 02 '16 at 06:27
@Sayse Of course it does! And your singletons look exactly like in all the books :) – egorikem Feb 02 '16 at 06:28
@GeorgySavatkow "alphanumeric"? – Christofer Ohlsson Feb 02 '16 at 07:31
@ChristoferOhlsson my bad then – egorikem Feb 02 '16 at 10:32

score -1 · Answer 2 · answered Feb 01 '16 at 10:02

In order for the ID to be truly unique you have to keep track of previously generated unique IDs, This can be simply done with a simple sqlite DB.

In order to generate a simple unique id use the following line:

import random
import string
u_id = ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(8))

More on strings can be found in the docs

Ahmed Hosny · Answer 3 · 2016-02-01T11:14:35.663

I suggest to make a token generator class like this:

import string, random
class RandomTokenGenerator(object):
    def __init__(self, chars=None, random_generator=None):
        self.chars = chars or string.ascii_uppercase + string.ascii_lowercase + string.digits
        self.random_generator = random_generator or random.SystemRandom()

    def make_token(self, n=20):
        return ''.join(self.random_generator.choice(self.chars) for _ in range(n))

token_generator = RandomTokenGenerator()

Then in your model should be like:

from django.db import models
from django.contrib.auth.models import User
from .token_utils import token_generator
    class Transfer(models.Model):
        id = models.AutoField(primary_key=True)
        user = models.ForeignKey(User)
        timestamp = models.DateTimeField(auto_now_add=True, auto_now=False)
        token = models.CharField(_('UUID'), max_length=8, null=False)
       def save(self, *args, **kwargs):
           ## This to check if it creates a new or updates an old instance
           if self.pk is None:
              self.token = token_generator.make_token(8)
           super(Transfer, self).save(*args, **kwargs)

score -1 · Answer 4 · answered Feb 01 '16 at 11:59

You could use the DB id and convert that to a sting using someting like this:

def int_to_key(num):
    if num == 0:
        return ""

    return "{0}{1}".format(
        int_to_key(num // 52), 
        '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'[num % 52]
    )

If you can adjust the code to use less or more characters as you need.

Django: Generate unique 8 character alphanumeric ID string on form submission

4 Answers4