addcart.py

class MyDict(dict):

	def __init__(self):
		self=dict()

	

	def addItem(self,key,value):
		if key in self:
			self[key] +=value
		else:
			self[key]=value


	def delItem(self,key,value):
		if key in self:
			self[key] -=value
	
					
	

myd=MyDict()
myd.addItem('apples',6)
myd.addItem('bananas',3)
myd.addItem('apples',4)
myd.delItem('apples',1)

print (myd)

carty.py

class Item(object):
	def __init__(self,unq_id,name,price,qty):
		self.unq_id=unq_id
		self.product_name=name
		self.price=price
		self.qty=qty


class Cart(object):
    def __init__(self):
        self.content = dict()

    def update(self, item):
        if item.unq_id not in self.content:
            self.content.update({item.unq_id: item})
            return
        for k, v in self.content.get(item.unq_id).items():
            if k == 'unq_id':
                continue
            elif k == 'qty':
                total_qty = v.qty + item.qty
                if total_qty:
                    v.qty = total_qty
                    continue
                self.remove_item(k)
            else:
                v[k] = item[k]

    def get_total(self):
        return sum([v.price * v.qty for _, v in self.content.items()])

    def get_num_items(self):
        return sum([v.qty for _, v in self.content.items()])

    def remove_item(self, key):
        self.content.pop(key)

    

    		


    	    


if __name__=='__main__':
	item1=Item(1,"Banana",1.,3)
	item2=Item(2,"Apple",2.5,2)
	cart=Cart()
	cart.update(item1)
	cart.update(item2)
	cart.remove_item(1)
	
	
	#print("you have %i items in your cart " , cart.get_num_items())
	print ("You have %i items in your cart for a total of $%.02f" %(cart.get_num_items(),cart.get_total()))