Compute bill, calcular grana

#-*- coding:utf-8 -*-

shopping_list = ["banana", "laranja", "maca"]

stock = { #FOOD, QUANTOS HÁ DE COMIDA
    "banana": 6,
    "maca": 0,
    "laranja": 32,
    "pera": 15
}

prices = { #PREÇOS
    "banana": 4,
    "maca": 2,
    "laranja": 1.5,
    "pera": 3
}

# Escreva seu codigo abaixo!

def compute_bill (food):
    total = 0
    for item in food:
        if (stock[item] > 0):
            total+=prices[item]
            stock[item]-=1
    print("Gastei %.2f reais na conta toda.\n" % (total))
    return(total)
compute_bill(stock)