bad operand type for abs(): 'str' in django
The currency filter expects its argument to be a numeric value; you're passing a string to your template as cart_sutotal. 
Before passing it to the template, convert it to a decimal.Decimal, or, better, figure out why you're adding up price values and coming up with a string for the subtotal.
I am going through the beginning django ecommerce application for shopping cart app. I am getting the error as mentioned above while clicking the add to cart button.
I am getting the error at the line {{ cart_sutotal|currency}}