django ajax project- basket - collecting values in array

Question

in my Django store I have a basket which in views.py has the class:

class BasketAddView(View):

    def post(self, request, *args, **kwargs):
        basket = Basket(request)
        product_id = str(request.POST.get('productid'))    
        product_size = str(request.POST.get('productsize'))
        product_qty = str(request.POST.get('productqty'))
        product = get_object_or_404(Product, id=product_id) #it was id and should be p
        basket_size_table = []
        basket_size_table.append(product_size)
        basket.add(product=product, size=product_size, qty = product_qty)
        basketqty=basket.__len__()
        response = JsonResponse({'size': basket_size_table,'product' : product_id, 'qty': basketqty, }) 
        return response

web inspector in output in console show that I have only last size in array:
[] 1

but I would like to have a collections of sizes in one array. Product_size is a single element, in html it is a select field with different values. I wish I could add these individual values ​​to the list of product with the same id but different sizes, example : product:"6" qty: 2 size: ['8/ϕ15mm/US5','7/ϕ14mm/US6']