Generate a Unique String in Python/Django

Question

What I want is to generate a string(key) of size 5 for my users on my website. More like a BBM PIN.

The key will contain numbers and uppercase English letters:

Answer 1

If you can afford to lose '8' and '9' in the generated numbers there is a very pythonic solution to getting a truly random number.

import os
import base64

base64.b32encode(os.urandom(3))[:5].decode('utf-8')

Since you are going for uniqueness then you have a problem since 36 * 36 * 36 * 36 * 36 = 60'466'176 which will definitely result in collisions if you have millions. Since sets are faster than dicts we do...

some_dict = set()

def generate():
    return base64.b32encode(os.urandom(3))[:5].decode('utf-8')

def generate_unique():
    string = generate()
    while string not in some_set:
        string = generate()
    some_set.add(string)
    return string

Answer 2

To generate unique one you can use below command:

import uuid 
str(uuid.uuid1())[:5]

Answer 3

My favourite is

import uuid 
uuid.uuid4().hex[:6].upper()

If you using django you can set the unique constrain on this field in order to make sure it is unique. https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.Field.unique

Answer 4

Am not sure about any short cryptic ways, but it can be implemented using a simple straight forward function assuming that you save all the generated strings in a set:

import random

def generate(unique):
    chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"
    while True:
        value = "".join(random.choice(chars) for _ in range(5))
        if value not in unique:
            unique.add(value)
            break

unique = set()
for _ in range(10):
    generate(unique)

Answer 5

A more secure and shorter way of doing is using Django's crypto module.

from django.utils.crypto import get_random_string
code = get_random_string(5)

get_random_string() function returns a securely generated random string, uses secrets module under the hood.

You can also pass allowed_chars:

from django.utils.crypto import get_random_string
import string

code = get_random_string(5, allowed_chars=string.ascii_uppercase + string.digits)

Answer 6

There is a function in django that does what you're looking for (credits to this answer):

Django provides the function get_random_string() which will satisfy the alphanumeric string generation requirement. You don't need any extra package because it's in the django.utils.crypto module.

>>> from django.utils.crypto import get_random_string
>>> unique_id = get_random_string(length=32)
>>> unique_id
u'rRXVe68NO7m3mHoBS488KdHaqQPD6Ofv'

You can also vary the set of characters with allowed_chars:

>>> short_genome = get_random_string(length=32, allowed_chars='ACTG')
>>> short_genome
u'CCCAAAAGTACGTCCGGCATTTGTCCACCCCT'