ShoppingCart.py

# ShoppingCart.py by gauravssnl

class ShoppingCart :
    def __init__( self ) :
        self.total = 0
        self.items = { }

    def add_item( self , item_name , quantity , price ) :
        self.total += quantity* price
        # set dictionary key to item_name and value to quantity
        self.items[ item_name ] = quantity

    def remove_item( self , item_name , quantity , price ) :
        if quantity > self.items[ item_name ] :
            self.total -= self.items[ item_name ] * price
            del self.items[item_name]
        else :
            self.total -= quantity * price
            self.items[ item_name ] -= quantity

    def checkout( self , cash_paid ) :
        if cash_paid >= self.total :
            return  cash_paid - self.total
        else :
            return "Cash paid not enough"


class Shop( ShoppingCart ) :
    def __init__( self ) :
        self.quantity = 100

    def remove_item(self ,quantity = 1 ) :
        self.quantity -= quantity

if __name__ == '__main__' :
    sc = ShoppingCart()

    # to check class attributes and to ensure methods are working correctly , we are printing them
    # printing attributes are optional

    # first argument is quantity ,second argument is price
    # add 50 items whose price is 30
    sc.add_item( 'NoteBook' , 50 , 30 )
    print( sc.items )
    print( sc.items['NoteBook'] )
    print( sc.total )
    #cash_paid is 2000 and is more than 1500 (50*30)
    print ( 'Balance : ')
    print( sc.checkout( 2000 ))

    # remove 10 items whose price is 30
    sc.remove_item('NoteBook' , 10 , 30)
    print( sc.items )
    print( sc.items['NoteBook'] )
    print( sc.total )

    #cash_paid is 1000 and Less than 1200 (40*30)

    print( sc.checkout(1000 ))
    # remove 41 items whose price is 30
    #item being removed is more than existing items ,so item NoteBook will be removed from dictionary
    sc.remove_item('NoteBook' , 41 , 30)
    print( sc.items )

    print( sc.total )