How do I fix this 'NoneType' error in my code?

Question

I'm just starting to learn python and have written a script with three functions. After the Q input is passed through I receive a Traceback error.

This is just a learning exercise so I can develop my Python skills. The learning module source code and my code appear to be exactly the same, but for some reason my output returns an error.

 File "C:\Users\Desktop\DearWorld\new.py", line 36, in <module>
    main()
  File "C:\Users\Desktop\DearWorld\new.py", line 33, in main
    total = bill_total(orders, menu)
  File "C:\Users\Desktop\DearWorld\new.py", line 24, in bill_total
    for order in orders:
TypeError: 'NoneType' object is not iterable

menu = {'Angel Dust Blunt': 6.66, 'The OG Blunt': 4.20, 'Caviar Blunt': 7.10, 'The Chronic Blunt' : 4.20}

def print_menu(menu):
    for name, price in menu.items():
        print(name, ': $', format(price, '.2f'), sep = '')

def get_order(menu):        
    orders = []
    order = input("What would you like to order (Q to quit)")

    while (order.upper()  != 'Q'):
    #Find the order and add it to the list if it exists
        found = menu.get(order)
        if found:
            orders.append(order)
        else:
            print("Menu item doesn't exist")

        order = input("Anything else? (Q to Quit)")

def bill_total(orders, menu):
    total = 0

    for order in orders:
        total += menu[order]

    return total

def main():
    menu = {'Angel Dust Blunt': 6.66, 'The OG Blunt': 4.20, 'Caviar Blunt': 7.10, 'The Chronic Blunt' : 4.20}
    print_menu(menu)
    orders = get_order(menu)
    total = bill_total(orders, menu)
    print("You ordered:" ,order, "Your total is: $", format(total, '.2f'), sep='')

main()

The script is supposed to return the bill_total and the items ordered as the output. What is returned instead when the user enters 'Q' is a 'TypeError'

Answer 1

Your get_order function isn't returning anything, so the value of orders in the line:

orders = get_order(menu)

will be None . Then you're trying to iterate over the variable, and it will fail.

You need to add this line at the end of the get_order function:

return orders

So the function should look like this:

def get_order(menu):        
    orders = []
    order = input("What would you like to order (Q to quit)")

    while (order.upper()  != 'Q'):
    #Find the order and add it to the list if it exists
        found = menu.get(order)
        if found:
            orders.append(order)
        else:
            print("Menu item doesn't exist")

        order = input("Anything else? (Q to Quit)")

    return orders  # Added this line

Answer 2

The reason is that orders is None , and it is because the function get_order returns nothing.

look at this line:

orders = get_order(menu)

you should add:

return orders

at the end of get_order function. like this:

def get_order(menu):        
    orders = []
    order = input("What would you like to order (Q to quit)")

    while (order.upper()  != 'Q'):
    #Find the order and add it to the list if it exists
        found = menu.get(order)
        if found:
            orders.append(order)
        else:
            print("Menu item doesn't exist")

        order = input("Anything else? (Q to Quit)")

    return orders

Answer 3

Your get_order() function has no return statement. As a result, it will always return None . Therefore, in main() :

orders = get_order(menu)
total = bill_total(orders, menu)

orders will get a value of None , which is then passed to bill_total() . When you try to iterate over that in the for loop, the result is the exception you're seeing

Answer 4

Late answer, but you can use:

menu = {
        "1": {"name":"Angel Dust Blunt", "price":6.66},
        "2": {"name":"The OG Blunt", "price":6.66},
        "3": {"name":"Caviar Blunt", "price":7.10},
        "4": {"name":"The Chronic Blunt", "price":4.20}
        }
orders = []

def print_menu():
    for k, v in menu.items():
        print(f"[{k}] - ", v['name'], ': $', format(v['price'], '.2f'), sep = '')

def bill_total():
    total = 0
    for id in orders:
        total += menu[id]['price']
    return total

def get_order():
    while 1:
        order = input(f"What would you like to order (Q to quit)\n")
        if order.strip().upper()  == 'Q':
            return
        else:
            found = menu.get(order)
            if found:
                # avoid dup orders, can be improved to increase the count of product items.
                if order in orders:
                    print("Product already in cart")
                    continue
                orders.append(order)
                print(f"Item {found['name']} added to cart")
            else:
                print("Menu item doesn't exist")

print_menu(), get_order(), print("You ordered:\n")
for id in orders:
    print(menu[id]['name'], f"${menu[id]['price']}")
print(f"\nYour total is: ${bill_total()}" )

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