Django : Generate unique slug

django_signals_slugify.py

# import signals and slugify
from django.db.models import signals
from django.template.defaultfilters import slugify


# function for use in pre_save
def yourmodel_pre_save(signal, instance, sender, **kwargs):
    if not instance.slug:
        slug = slugify(instance.attribute)  # change the attibute to the field that would be used as a slug
        new_slug = slug
        count = 0
        while YourModel.objects.filter(slug=new_slug).exclude(id=instance.id).count() > 0:
            count += 1
            new_slug = '{slug}-{count}'.format(slug=slug, count=count)
        
        instance.slug = new_slug

# Execute signals pre_save
signals.pre_save.connect(your_model_pre_save, sender=YourModel)

this method can be useful when adding only one more similar slug because the count variable will be always 1 since it will be reset to 0 whenever the method is invoked.
You will face race condition when you have 3 similar attribute (instance.attribute).

@Radi85 Today I really think the best approach is use the primary_key instead count on post save.