Question

为什么我收到此错误？图片有详细信息。我需要让_spent值打印适当的次数。所以，比如它经过循环3次，我需要它打印3.我认为这是1来自哪里。我不喜欢它！

pennies = 10
nickels = 10
dimes = 10
quarters = 10

print("\nWelcome to change-making program.")
in_str = input("\nEnter the purchase price (xx.xx) or `q' to quit: ")

while in_str.lower() != 'q':
    dollar_str, cents_str = in_str.split(".")

    if in_str.lower() == 'q':
        quit()

    in_int = int(float(in_str) * 100)

    if in_int < 0:
        print("Error: purchase price must be non-negative.")
        in_str = input("\nEnter the purchase price (xx.xx) or `q' to quit: ")

    if in_int > 0:
        payment = input("\nInput dollars paid: ")
        payment_int = int(float(payment) * 100)
        change = payment_int - in_int

        #determines if there payment input
        if payment_int < in_int:
            print("Error: Insufficient payment.")
            payment = input("\nInput dollars paid: ")
            payment_int = int(float(payment) * 100)


        if change == 0:
            print("No change.")

        #determines how many quarters, dimes, nickels, and pennies are left
        while change >= 25 and quarters > 0:
            change = change - 25
            quarters_spent = 0
            quarters_spent += 1
            quarters = quarters - quarters_spent
        print(quarters_spent)

        while change >= 10 and dimes > 0:
            change = change - 10
            dimes_spent = 0
            dimes_spent += 1
            dimes = dimes - dimes_spent
        print(dimes_spent)

        while change >= 5 and nickels > 0:
            change = change - 5
            nickels_spent = 0
            nickels_spent += 1
            nickels = nickels - nickels_spent
        print(nickels_spent)

        while change >= 1 and pennies > 0:
            change = change - 1
            pennies_spent = 0
            pennies_spent += 1
            pennies = pennies - pennies_spent

        if quarters == 0 and dimes == 0 and nickels == 0 and pennies == 0:
            print("Error: ran out of coins.")
            quit()

        print("\nCollect Payment Below:")
        print(10 - quarters, "Quarters")

        print("\nStock: ", quarters, "Quarters, ", dimes, " Dimes, ", nickels, " Nickels, ", pennies, " Pennies ")

        in_str = input("\nEnter the purchase price (xx.xx) or `q' to quit: ")

        pennies = pennies
        nickels = nickels
        dimes = dimes
        quarters = quarters

Answer 1

此错误表示您在尝试使用之前未定义值nickels_spent。

我猜错误就在这一行：print (nickels_spent)。

可能发生的情况是，当您尝试运行该变量时，用于为该变量赋值的while语句条件不正确，因此它尚未定义，但您仍尝试用它。

在while循环之前尝试调试，看看到底发生了什么。

Answer 2

您只在while循环

中定义并初始化了此变量nickels_spent

但是，如果不满足条件，程序将跳过循环并跳转以执行此print(nickels_spent)语句，其中此变量尚未定义。

你可以

将print语句移动到while循环

或者

在while循环之外定义并初始化此变量。

取决于您的计划的目的

为什么我会收到此错误＆＃34;名称未定义＆＃34;几时？

2 个答案: