Django Carton

  +------+
 /|     /|
+-+----+ |    django-carton is a simple and lightweight application
| |    | |    for shopping carts and wish lists.
| +----+-+
|/     |/
+------+

Simple: You decide how to implement the views, templates and payment processing.
Lightweight: The cart lives in the session.
Just a container: You define your product model the way you want.

Usage Example

View:

from django.http import HttpResponse

from carton.cart import Cart
from products.models import Product

def add(request):
    cart = Cart(request.session)
    product = Product.objects.get(id=request.GET.get('product_id'))
    cart.add(product, price=product.price)
    return HttpResponse("Added")

def show(request):
    return render(request, 'shopping/show-cart.html')

We are assuming here that your products are defined in an application called products.

Template:

{% load carton_tags %}
{% get_cart as cart %}

{% for item in cart.items %}
    {{ item.product.name }}
    {{ item.quantity }}
    {{ item.subtotal }}
{% endfor %}

You can also use this convinent shortcut:
{% for product in cart.products %}
    {{ product.name }}
{% endfor %}

Within the template you can access the product id with {{product.id}}.

Settings:

CART_PRODUCT_MODEL = 'products.models.Product'

This project is shipped with an application example called shopping implementing basic add, remove, display features. To use it, you will need to install the shopping application and include the URLs in your project urls.py

# settings.py
INSTALLED_APPS = (
    'carton',
    'shopping',
    'products',
)

# urls.py
urlpatterns = patterns('',
    url(r'^shopping-cart/', include('shopping.urls')),
)

Assuming you have some products defined, you should be able to add, show and remove products like this:

/shopping-cart/add/?id=1
/shopping-cart/show/
/shopping-cart/remove/?id=1

Installation

This application requires Django version 1.4; all versions above should be fine.

Just install the package using something like pip and add carton to your INSTALLED_APPS setting.

Add the CART_PRODUCT_MODEL setting, a dotted path to your product model.

This is how you run tests:

./manage.py test carton.tests --settings=carton.tests.settings

Abstract

The cart is an object that's stored in session. Products are associated to cart items.

Cart
|-- CartItem
|----- product
|----- price
|----- quantity

A cart item stores a price, a quantity and an arbitrary instance of a product model.

You can access all your product's attributes, for instance it's name:

{% for item in cart.items %}
    {{ item.price }}
    {{ item.quantity }}
    {{ item.product.name }}
{% endfor %}

Managing Cart Items

These are simple operations to add, remove and access cart items:

>>> apple = Product.objects.all()[0]
>>> cart.add(apple, price=1.5)
>>> apple in cart
True
>>> cart.remove(apple)
>>> apple in cart
False

>>> orange = Product.objects.all()[1]
>>> cart.add(apple, price=1.5)
>>> cart.total
Decimal('1.5')
>>> cart.add(orange, price=2.0)
>>> cart.total
Decimal('3.5')

Note how we check weather the product is in the cart - The following statements are different ways to do the same thing:

>>> apple in cart
>>> apple in cart.products
>>> apple in [item.product for item in cart.items]

The "product" refers to the database object. The "cart item" is where we store a copy of the product, it's quantity and it's price.

>>> cart.items
[CartItem Object (apple), CartItem Object (orange)]

>>> cart.products
[<Product: apple>, <Product: orange>]

Clear all items:

>>> cart.clear()
>>> cart.total
0

Increase the quantity by adding more products:

>>> cart.add(apple, price=1.5)
>>> cart.add(apple)  # no need to repeat the price.
>>> cart.total
Decimal('3.0')

Note that the price is only needed when you add a product for the first time.

>>> cart.add(orange)
*** ValueError: Missing price when adding a cart item.

You can tell how many items are in your cart:

>>> cart.clear()
>>> cart.add(apple, price=1.5)
>>> cart.add(orange, price=2.0, quantity=3)
>>> cart.count
4
>>> cart.unique_count  # Regarless of product's quantity
2

You can add several products at the same time:

>>> cart.clear()
>>> cart.add(orange, price=2.0, quantity=3)
>>> cart.total
Decimal('6')
>>> cart.add(orange, quantity=2)
>>> cart.total
Decimal('10')

The price is relevant only the first time you add a product:

>>> cart.clear()
>>> cart.add(orange, price=2.0)
>>> cart.total
Decimal('2')
>>> cart.add(orange, price=100)  # this price is ignored
>>> cart.total
Decimal('4')

Note how the price is ignored on the second call.

You can change the quantity of product that are already in the cart:

>>> cart.add(orange, price=2.0)
>>> cart.total
Decimal('2')
>>> cart.set_quantity(orange, quantity=3)
>>> cart.total
Decimal('6')
>>> cart.set_quantity(orange, quantity=1)
>>> cart.total
Decimal('2')
>>> cart.set_quantity(orange, quantity=0)
>>> cart.total
0
>>> cart.set_quantity(orange, quantity=-1)
*** ValueError: Quantity must be positive when updating cart

Removing all occurrence of a product:

>>> cart.add(apple, price=1.5, quantity=4)
>>> cart.total
Decimal('6.0')
>>> cart.remove(apple)
>>> cart.total
0
>>> apple in cart
False

Remove a single occurrence of a product:

>>> cart.add(apple, price=1.5, quantity=4)
>>> cart.remove_single(apple)
>>> apple in cart
True
>>> cart.total
Decimal('4.5')
>>> cart.remove_single(apple)
>>> cart.total
Decimal('3.0')
>>> cart.remove_single(apple)
>>> cart.total
Decimal('1.5')
>>> cart.remove_single(apple)
>>> cart.total
0

Multiple carts

Django Carton has support for using multiple carts in the same project. The carts would need to be stored in Django session using different session keys.

from carton.cart import Cart

cart_1 = Cart(session=request.session, session_key='CART-1')
cart_2 = Cart(session=request.session, session_key='CART-2')

Working With Product Model

Django Carton needs to know how to list your product objects.

The default behaviour is to get the product model using the CART_PRODUCT_MODEL setting and list all products.

The default queryset manager is used and all products are retrieved. You can filter products by defining some lookup parameters in CART_PRODUCT_LOOKUP setting.

# settings.py

CART_PRODUCT_LOOKUP = {
    'published': True,
    'status': 'A',
}

If you need further customization of the way product model and queryset are retrieved, you can always sub-class the default Cart and overwrite the get_queryset method. In that case, you should take into account that:

You probably won't need CART_PRODUCT_MODEL and CART_PRODUCT_LOOKUP if you get a direct access to your product model and define the filtering directly on the cart sub-class.
You probably have to write your own template tag to retrieve the cart since the default get_cart template tag point on the Cart class defined by django-carton.

Settings

Template Tag Name

You can retrieve the cart in templates using {% get_cart as my_cart %}.

You can change the name of this template tag using the CART_TEMPLATE_TAG_NAME setting.

# In you project settings
CART_TEMPLATE_TAG_NAME = 'get_basket'

# In templates
{% load carton_tags %}
{% get_basket as my_basket %}

Stale Items

Cart items are associated to products in the database. Sometime a product can be found in the cart when its database instance has been removed. These items are called stale items. By default they are removed from the cart.

Session Key

The CART_SESSION_KEY settings controls the name of the session key.

tuxo/django-carton