gistfile1.py

class ShortUrlModelMixin(models.Model):
    TOKEN_LEN = 5
    short_url = models.CharField(max_length=TOKEN_LEN, db_index=True, unique=True, editable=False)

    class Meta:
        abstract = True

    def save(self, *args, **kwargs):
        if not self.pk:
            while 1:
                self.short_url = self.gen_token()
                try:
                    self._meta.model.objects.get(short_url=self.short_url)
                except self._meta.model.DoesNotExist:
                    break
            super(ShortUrlModelMixin, self).save(*args, **kwargs)

    def gen_token(self):
        token_src = binascii.b2a_base64(str(random.randrange(0, 1000000)).encode('utf-8'))[:-3]
        return ''.join(random.sample(str(token_src).replace("'", ""), self.TOKEN_LEN)).lower()