Class and objects in Python

Question

I'm running a simple online shopping cart program and when I tried to run it, the ending result was blank. I understand the concept about classes and objects, but I really need assistance. It is supposed to look like this:

Item 1
Enter the item name: Chocolate Chips
Enter the item price: 3
Enter the item quantity: 1

Item 2
Enter the item name: Bottled Water
Enter the item price: 1
Enter the item quantity: 10

TOTAL COST
Chocolate Chips 1 @ $3 = $3
Bottled Water 10 @ $1 = $10

Total: $13

Here's what I've written so far, :

class ItemsToPurchase :

    def __init__(self, item_name = "none", item_price = 0, item_quantity = 0):
        self.item_name = item_name
        self.item_price = item_price
        self.item_quantity = item_quantity

    def print_item_cost(self):
        total = item_quantity * item_price
        print('%s %d @ $%f = $%f' % (item_name, item_quantity, item_price, total))

def main():

    print('Item 1')
    print()

    item_name = str(input('Enter the item name: '))
    item_price = float(input('Enter the item price: '))
    item_quantity = int(input('Enter the item quantity: '))

    item_one = ItemsToPurchase(item_name, item_price, item_quantity)
    item_one.print_item_cost()

    print('Item 2')
    print()

    item_name = str(input('Enter the item name: '))
    item_price = float(input('Enter the item price: '))
    item_quantity = int(input('Enter the item quantity: '))

    item_two = ItemsToPurchase(item_name, item_price, item_quantity)
    item_two.print_item_cost()

    print('TOTAL COST')
    item_one.print_item_cost()
    item_two.print_item_cost()

if __name__ == "__main__":
    main()

What did I do wrong?

Not sure if this is just in you asking the question but, the call to main() isn't indented under the if statement — Sighonide
– Sighonide, Commented Nov 30, 2016 at 4:47
The print_item_cost method has a problem. you may have to prefix the variables item_name,item_quantity,item_price with the self keyword to access the corresponding class variables. Something like self.variable_name. — Parthipan Natkunam
– Parthipan Natkunam, Commented Nov 30, 2016 at 4:56
I suppose your issue is resolved, please mark the answer as accepted. @JohnWalker — Jarvis
– Jarvis, Commented Nov 30, 2016 at 6:07

Jarvis · Accepted Answer · 2016-11-30 04:50:54Z

3

You have some issues in your print_item_cost method, it should be like this :

def print_item_cost(self):
    total = self.item_quantity * self.item_price
    print('%s %d @ $%f = $%f' % (self.item_name, self.item_quantity, self.item_price, total))

You refer to a class attribute like this : self.attr

answered Nov 30, 2016 at 4:50

Jarvis

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3 Comments

Sighonide Over a year ago

If the above has solved it, ignore this: Assuming you are running this in a child process (assuming as this is used: if __name__ == "__main__":), then you might need to flush sys.stdout by calling sys.stdout.flush() in the above code (after you've called all your print functions). This is due to the output of the child process being buffered. Ignore this if you aren't using multiple processes

Jarvis Over a year ago

There is no mention of multi-programming as far as I know, and as far as I know using __name__ == "main" is a common thing. There were other issues in the OP's code. You can see my answer and check that for yourself. (and hopefully upvote it too :) ) @Sighonide

Sighonide Over a year ago

I agreed with your answer :) I was only covering all bases as __name__ == "main" might suggest multiprocessing. But now that I think about it, he probably just wants to be able to import the class and function definition without running main() as well as be able to run it all from scratch : / lol

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