How to extend django cart functionality?

Question

Django

In general, there is a site in python with django and a map module.
I want to implement functionality + 1 product, - 1 product.
HTML

<form class="cart-button" action="/cartminus/" method="GET">
            <input name="product_id" type="hidden" value="{{ item.product.id }}">
            <input name="quantity" type="hidden" value="{{ item.quantity }}">
            <input class="cart-button-plus" type="submit" value="-">
       </form> 
       <div id="cartAm">{{ item.quantity }}</div>
       <form class="cart-button" action="/cartplus/" method="GET">
            <input name="product_id" type="hidden" value="{{ item.product.id }}">
            <input name="quantity" type="hidden" value="{{ item.quantity }}">
            <input class="cart-button-minus" type="submit" value="+">
       </form>

And in python it looks like this

from django.shortcuts import render, render_to_response
from django.http import HttpResponse, HttpResponseRedirect
from cart import Cart
from spares.models import Goods, ExchangeRate
from users.views import getCart
from django.core.urlresolvers import reverse

def cartminus(request):
    product_id = request.GET['product_id']
    quantity = request.GET['quantity'] 
    cart = Cart(request)
    for item in cart:
        if item.product.id == product_id:
           item.quantity = int(quantity) - int(1)
           item.save()
    return HttpResponseRedirect('/trash/')

def cartplus(request):
    product_id = request.GET['product_id']
    quantity = request.GET['quantity'] 
    cart = Cart(request)
    for item in cart:
        if item.product.id == product_id:
           item.quantity = int(quantity) + int(1)
           item.save()
    return HttpResponseRedirect('/trash/')

Doesn't work, when you click on the buttons, just refreshes the page and that's it? Any advice, suggestions, what to read?

Answer 1

UPD I solved it

def cartminus(request):
    product_id = request.GET['product_id']
    product = Goods.objects.get(id=product_id)
    quantity = request.GET['quantity'] 
    cart = Cart(request)
    for item in cart:
        if item.product.id == product.id:
           quantity = int(item.quantity) - int(1)
           if quantity == 0:
                item.delete()
           else:
                item.quantity = int(quantity)
                item.save()
    return HttpResponseRedirect('/trash/')

def cartplus(request):
    product_id = request.GET['product_id']
    product = Goods.objects.get(id=product_id)
    quantity = request.GET['quantity'] 
    cart = Cart(request)
    for item in cart:
        if item.product.id == product.id:
           quantity = int(item.quantity) + int(1)
           if quantity == 0:
                item.delete()
           else:
                item.quantity = int(quantity)
                item.save()
    return HttpResponseRedirect('/trash/')