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 have a way of associating each user to a unique ID (for example Primary Key in Django or Flask). You can do something like this:

Note: This does not generate a fixed length.

We will pad the user_id to the right to make the generated length a bit static

import os
import base64

user_id = 1

#pad the string
number_generate = str(user_id).rjust(5,"0")

base64.b32encode(bytes(number_generate, 'utf-8')).decode('utf-8').replace('=','')

Answer 2

size = 5
''.join(random.choice(string.letters[26:] + string.digits) for in range(size))

this will generate some short code, but they can be duplicated. so check if they are unique in your database before saving.

def generate(size=5):
    code = ''.join(random.choice(string.letters[26:] + string.digits) for in range(size))
    if check_if_duplicate(code):
        return generate(size=5)
    return code

or using django unique constrain, and handle exceptions.

Answer 3

I have a unique field, named 'systemCode' within a lot of my models. And I am generating this manually, but also sometimes it can take value from user input, so I have to check this value before saving and if it matches , regenerating this value as a unique value.

And this is how I generate unique strings at this scenario :

---

This is my standard class Model :

class ClassOne(models.Model):
   name = models.CharField(max_length=100)
   systemCode = models.CharField(max_length=25, blank=True, null=True, unique=True)
   ....

I am using save() method to generate and check this systemCode is unique :

    def save(self, *args, **kwargs):
        systemCode = self.systemCode
        if not systemCode:
            systemCode = uuid.uuid4().hex[:6].upper()
        while ClassOne.objects.filter(systemCode=systemCode).exclude(pk=self.pk).exists():
            systemCode = uuid.uuid4().hex[:6].upper()
        self.systemCode = systemCode
        super(ClassOne, self).save(*args, **kwargs)

But I have same systemCode field in all my Models. So I am using a function to generate value.

So, this is how to generate unique value for all models using saveSystemCode() function :

import uuid 

def saveSystemCode(inClass, inCode, inPK, prefix):
    systemCode = inCode
    if not systemCode:
        systemCode = uuid.uuid4().hex[:6].upper()

    while inClass.objects.filter(systemCode=systemCode).exclude(pk=inPK).exists():
        systemCode = uuid.uuid4().hex[:6].upper()

    return systemCode

class ClassOne(models.Model):
    name = models.CharField(max_length=100)
    systemCode = models.CharField(max_length=25, blank=True, null=True, unique=True)
    ....

    def save(self, *args, **kwargs):
        self.systemCode = saveSystemCode(ClassOne, self.systemCode, self.pk, 'one_')
        super(ClassOne, self).save(*args, **kwargs)


class ClassTwo(models.Model):
    name = models.CharField(max_length=100)
    systemCode = models.CharField(max_length=25, blank=True, null=True, unique=True)
    ....

    def save(self, *args, **kwargs):
        self.systemCode = saveSystemCode(ClassTwo, self.systemCode, self.pk, 'two_')
        super(ClassTwo, self).save(*args, **kwargs)

class ClassThree(models.Model):
    name = models.CharField(max_length=100)
    systemCode = models.CharField(max_length=25, blank=True, null=True, unique=True)
    ....

    def save(self, *args, **kwargs):
        self.systemCode = saveSystemCode(ClassThree, self.systemCode, self.pk, 'three_')
        super(ClassThree, self).save(*args, **kwargs)

---

while loop in the 'saveSystemCode' function is preventing to save same value again.

Answer 4

From 3.6 You can use secrets module to generate nice random strings. https://docs.python.org/3/library/secrets.html#module-secrets

import secrets
print(secrets.token_hex(5))