Django Admin model create new instance instead of update

Question

I've multiple models in my Django project but only this given below model creating another instance on update instead of save. This is happening in Django's Admin panel, not on my custom UI. When I remove my save() method then it works fine but this way I won't be able to create slug .

Does anybody know what I'm doing wrong in here

class Course(models.Model):
    title = models.CharField(max_length=200)
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    category = models.ForeignKey(Category, on_delete=models.SET_NULL, null=True, related_name='category')
    slug = models.SlugField(max_length=200, unique=True, primary_key=True, auto_created=False)
    short_description = models.TextField(blank=False, max_length=60)
    description = models.TextField(blank=False)
    outcome = models.CharField(max_length=200)
    requirements = models.CharField(max_length=200)
    language = models.CharField(max_length=200)
    price = models.FloatField(validators=[MinValueValidator(9.99)])
    level = models.CharField(max_length=20)
    application_link = models.URLField(max_length=1000, blank=True, null=True)
    brochure = models.FileField(upload_to='brochures/', blank=True, null=True)
    thumbnail = models.ImageField(upload_to='thumbnails/')
    video_url = models.CharField(max_length=100)
    is_session_available = models.BooleanField(default=False)
    session_url = models.CharField(max_length=250, default='')
    is_published = models.BooleanField(default=True)
    created_at = models.DateTimeField(default=now)
    updated_at = models.DateTimeField(default=now)

    def __str__(self):
        return self.title

    def save(self, *args, **kwargs):
        self.slug = slugify(self.title)
        super(Course, self).save(*args, **kwargs)

Answer 1

instead of overriding save method you could do this:

admin.py

class CourseAdmin(admin.ModelAdmin):
    prepopulated_fields = {'slug': ('title',)}

admin.site.register(Course, CourseAdmin)

Answer 2

It is happening because it will generate new slug every time. You can do something like this:

    def generate_slug(self):
        self.slug = slugify(self.name)

    def save(self, *args, **kwargs):
        if not self.slug:
            self.generate_slug() # This will generate slug.

        return super().save(*args, **kwargs)