Django Set & Retrieve Session Data

Question

Im working on an eCommerce website using Django. Currently working on the cart app where im using session in django for the first time. Im having problems with setting and retrieving session data which is empty when i print it.

PS: the data from the session will be used to retrieve the cart for the user or update the cart if the cart was created as a visitor.

Not being able to retrieve session data result in a new session being created every time i refresh the browser.

SETTINGS.PY

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',

    # user apps
    'carts',
    'products',
    'search',
    'tags',

    # 3rd class app
    'bootstrap4',
]

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

CART APP

MODELS.PY

from django.conf import settings
from django.db import models

from products.models import Product

User = settings.AUTH_USER_MODEL


class CartManager(models.Manager):
    def new(self, user=None):
        user_obj = None
        if user is not None:
            if user.is_authenticated:
                user_obj = user
        return self.model.objects.create(user=user_obj)

class Cart(models.Model):
    user        = models.ForeignKey(User, null=True, blank=True, on_delete=models.DO_NOTHING)
    products    = models.ManyToManyField(Product, blank=True)
    total       = models.DecimalField(default=0.00, max_digits=100, decimal_places=2)
    timestamp   = models.DateTimeField(auto_now_add=True)
    updated     = models.DateTimeField(auto_now=True)

    objects = CartManager()

    def __str__(self):
        return str(self.id)

VIEWS.PY

from django.shortcuts import render

from .models import Cart


def cart_home(request):
    cart_id = request.session.get('cart_id')
    qs = Cart.objects.filter(id=cart_id)
    print(cart_id, qs)
    # print(dir(request.session))
    if qs.count() == 1:
        print('Cart ID exists')
        cart_obj = qs.first()
        if request.user.is_authenticated and cart_obj.user is None:
            cart_obj.user = request.user
            cart_obj.save()
    else:
        cart_obj = Cart.objects.new(user=request.user)
        request.session['card_id']  = cart_obj.id
        # request.session.modified = True
        # print(dir(request.session))
        # print(request.session.get_expiry_age())
    return render(request, 'carts/home.html', {})

Answer 1

I think your problem might be a typo in this line:

request.session['card_id']  = cart_obj.id

If you look closely you are setting a card_id but are later trying to fetch a cart_id.