TypeError:“NoneType”对象对于MIT Opencourse Assignmen不可编辑

Question

尝试在麻省理工学院开放式课件sc6.00上提问。 问题是如何找到6，9，20包的麦金块组合，并给出总数量。 目前我的代码是：

def Mac ():
    totalnumber = int (input('Enter total number of McNuggets'))
    num20,num6,num9= solve2(totalnumber)

def solve2(numtotal): #define a new function to find and print multiple answers
    solutionfound = False # set up a variable to check if the solution is found
    for num20 in range (0,numtotal//20 + 1):
        for num9 in range (0,numtotal//9 +1):
            num6 = (numtotal-num20*20-num9*9)//6
            if num6 > 0:
                checknum = num20*20+num9*9+num6*6
                if checknum == numtotal:
                    print ('The number of 6-pack is', num6)
                    print ('The number of 9-pack is', num9)
                    print ('The number of 20-pack is', num20)
                    solutionfound = True # change the initial variable to True
    if not solutionfound:
        print ('There is no solution')

但是，运行此代码时，它始终显示：

TypeError: 'NoneType' object is not iterable

Answer 1

函数solve2()不返回任何值，因此它的返回值是None，您正试图通过执行num20,num6,num9= solve2(totalnumber)来迭代它。所以这部分代码会引发TypeError: 'NoneType' object is not iterable。在

查看代码，我无法决定从何处返回值，因此无论您想返回值，只要使用return。在

Answer 2

你可以试试这个：

def Mac ():
    totalnumber = int (input('Enter total number of McNuggets: '))
    num20,num6,num9 = solve2(totalnumber)

def solve2(numtotal): #define a new function to find and print multiple answers
    solutionfound = False # set up a variable to check if the solution is found
    for num20 in range (0,numtotal//20 + 1):
        for num9 in range (0,numtotal//9 +1):
            num6 = (numtotal-num20*20-num9*9)//6
            if num6 > 0:
              checknum = num20*20+num9*9+num6*6
              if checknum == numtotal:
                  print ('The number of 6-pack is', num6)
                  print ('The number of 9-pack is', num9)
                  print ('The number of 20-pack is', num20)
                  solutionfound = True # change the initial variable to True
                  return (num6, num9, num20)
    if not solutionfound:
        print ('There is no solution')
        return (None, None, None)

Mac()

正确地指出，您需要从方法solve2返回值。在