def update_category(request):

    if request.method=='POST':
        old_name=request.POST.get('old_name').strip() # get old name
        new_name=request.POST.get('new_name').strip() # get new name
        categorie=Category.objects.get(title=old_name) # get category by title (pk)
        categorie.title=new_name # update the title
        categorie.save() # save to the database

return HttpResponseRedirect('/admin/Category_Management)

class Category(models.Model):
    class Meta:
        verbose_name='Catégorie'
        verbose_name_plural='Catégories'

    title=models.CharField(primary_key=True,max_length=50,null=False,blank=False,verbose_name='Titre')

    def __str__(self):
        return self.title.title()

class Category(models.Model):
    class Meta:
        verbose_name='Catégorie'
        verbose_name_plural='Catégories'

    title=models.CharField(max_length=50,null=False,blank=False,verbose_name='Titre')

    def __str__(self):
        return self.title.title()

category = Category.objects.get(title='test')
category.id = None
category.title = 'new test'
category.save() # it will make another category, with title 'new test'