Prodavnica

userFile = "prodavci.txt"
productFile = "proizvodi.txt"
delimiter = "|"
sentinel = "quit"

def loadUsers():
    fUsers = open(userFile, "r")

    for user in fUsers.readlines():
        user = user[:-1]
        user = user.split(delimiter)
        users.append(user)

    fUsers.close()

def logIn(username, password):
    for user in users:
        if username == user[0] and password == user[1]:
            return True

    return False

def inputLogIn():
    username = input("Unesite korsnicko ime: ")
    password = input("Unesite lozinku: ")

    return logIn(username, password)

users = []
loadUsers()

def addProduct(name, price, amount):
    products.append([name, price, amount])

def loadProducts():
    try:
        fProducts = open(productFile, "r")

        for product in fProducts.readlines():
            product = product[:-1]
            product = product.split(delimiter)
            addProduct(product[0], float(product[1]), int(product[2]))

        fProducts.close()
    except IOError:
        pass

def saveProduct(name, price, amount):
    fProducts = open(productFile, "a")

    productLine = name + delimiter + str(price) + delimiter + str(amount)+ "\n"
    fProducts.write(productLine)

    fProducts.close()

def inputProduct():
    while True:
        name = input("Unestie naziv: ")
        if name == sentinel:
            return False
        elif name == "":
            print("Neispravan unos! Naziv ne sme biti prazan.")
            continue
        break

    while True:
        price = input("Unesite cenu: ")
        if price == sentinel:
            return False
        try:
            price = float(price)
        except ValueError:
            print("Neispravan unos! Cena mora biti broj.")
            continue
        if price <= 0:
            print("Neispravan unos! Cena mora biti pozitivan broj.")
            continue
        break

    while True:
        amount = input("Unesite kolicinu: ")
        if amount == sentinel:
            return False
        try:
            amount = int(amount)
        except ValueError:
            print("Neispravan unos! Kolicina mora biti ceo broj.")
            continue
        if amount < 0:
            print("Neispravan unos! Kolicina ne sme biti negativan broj.")
            continue
        break

    addProduct(name, price, amount)
    saveProduct(name, price, amount)

    return True

def listProducts():
    print("\nProizvodi:")
    print("----------------------------")
    print("{0:<10}{1:<10}{2:<10}".format("Naziv", "Cena", "Kolicina"))

    print("----------------------------")
    for product in products:
        print("{0:<10}{1:<10.2f}{2:<10}".format(product[0], product[1], product[2]))

products = []
loadProducts()

def main():
    print("Prodavnica")
    print("----------")

    print("\nPrijava na sistem...")
    while not inputLogIn():
        print("\nNeuspesna prijava!")

    while True:
        listProducts()

        print("\nUnos novog proizovda...")
        if not inputProduct():
            print("\nPrekid programa!")
            break

main()