python - 类型错误 : 'NoneType' object is not iterable

Question

我在“companyName, monthAverage, costPerTon, totalCost = displayCost(companyName, monthAverage, costPerTon, totalCost)”这一行收到“TypeError: 'NoneType' object is not iterable”，我这辈子都做不到找出原因。

抱歉，我似乎无法正确格式化...

4-25-11最终项目，全局垃圾计划

主要功能

def main():

    #intialize variables
    endProgram = 'no'
    companyName = 'NONAME'

    #call to input company name
    companyName = inputName(companyName)

    #start 'end program' while loop
    while endProgram == 'no':

        #initializes variables
        companyName = 'NONAME'
        monthAverage = 0
        costPerTon = 0
        totalCost = 0
        yearTotal = 0

        #call to input company name
        companyName = inputName(companyName)

        #call to get the tonnage
        yearTotal, monthAverage = getTonnage(yearTotal, monthAverage)

        #call to calculate the cost
        monthAverage, costPerTon, totalCost, yearTotal = calculateCost(monthAverage, costPerTon, totalCost, yearTotal)

        #call to display the cost
        companyName, monthAverage, costPerTon, totalCost = displayCost(companyName, monthAverage, costPerTon, totalCost)

        endProgram = raw_input('Do you want to end the program? (enter yes or no)')

获取公司名称

def inputName(companyName):
    companyName = raw_input('What is the name of your company? ')
    return companyName

获取吨位

def getTonnage(yearTotal, monthAverage):
    yearTotal = input('How many tons of garbage are you dumping this year? ')
    monthAverage = yearTotal / 12
    return yearTotal, monthAverage

计算调用

def calculateCost(monthAverage, costPerTon, totalCost, yearTotal):
    if monthAverage > 100:
        costPerTon = 7000
    elif monthAverage > 50:
        costPerTon = 6500
    elif monthAverage > 20:
        costPerTon = 5500
    else:
        costPerTon = 4500
    totalCost = costPerTon * yearTotal
    return monthAverage, costPerTon, totalCost, yearTotal

打印成本

def displayCost(companyName, monthAverage, costPerTon, totalCost):
    print 'Dear',companyName
    print 'The average tonnage per month is ', monthAverage
    print 'The cost per ton is $',costPerTon
    print 'The total the is the cost per ton times total tons $',totalCost

运行主程序

main()

Answer 1

您尝试将 displayCost 的返回值解包为 4 个变量，但 displayCost 没有返回任何内容。因为每个函数调用在 Python 中都会返回一些东西(或抛出异常)，所以不会返回 None。那么 None 是无法解包的。

你可能想改变:

companyName, monthAverage, costPerTon, totalCost = displayCost(companyName, monthAverage, costPerTon, totalCost)

收件人:

displayCost(companyName, monthAverage, costPerTon, totalCost)