def shopping_cart():
	
	"""
	This is the user's shopping cart. All courses that
	the user will buy (free or not) are recorded in a
	session until the Buy Now action.
	"""

	classes = []
	amount = 0
	for class_id in session.cart:
		cart_class = Class(id=class_id)
		classes.append(cart_class)
		amount += cart_class.course.discount-cart_class.course.price

	return dict(classes=classes,
				amount=amount)
dataset/ETHPy150Open juliarizza/web2courses/controllers/payments.py/shopping_cart/swapped operands of `-`