计划提前终止，比我预期的要早

Question

我正在处理一个 MyProgrammingLab 问题，该问题陈述如下：

您在一家出售两种商品的面包店工作：松饼和纸杯蛋糕。在任何给定时间，您商店中的松饼和纸杯蛋糕的数量都存储在为您定义的变量松饼和纸杯蛋糕中。 编写一个程序，从标准输入中获取字符串，指示您的客户正在购买什么（“松饼”代表松饼，“纸杯蛋糕”代表纸杯蛋糕）。如果他们买松饼，减少一个松饼，如果他们买一个纸杯蛋糕，减少一个纸杯蛋糕。如果没有更多的烘焙食品，请打印（“缺货”）。

完成销售后，输入“0”，然后让程序打印出剩余的松饼和纸杯蛋糕的数量，格式为“松饼：9 个纸杯蛋糕：3”（如果剩下 9 个松饼和 3 个纸杯蛋糕，例如）。

我正在 jGRASP 中测试我的代码（不是粉丝，不幸的是课程需要）并且程序按预期工作，但有时它似乎提前终止，我正在努力找出原因，因为我不能在我的逻辑中找到任何错误。这是我所拥有的：

muffins = 5
cupcakes = 6
buyItem = raw_input("")
while buyItem == "m":
   if muffins <= 0:
      if cupcakes <= 0:
         print("All out of stock.")
         break
      else:
         print("Out of stock.")
         buyItem = raw_input("")
   else:
      muffins -= 1
      print("muffins: {} cupcakes: {}".format(muffins, cupcakes))
      buyItem = raw_input("")
while buyItem == "c":
   if cupcakes <= 0:
      if muffins <=0:
         print("All out of stock.")
         break
      else:
         print("Out of stock.")
         buyItem = raw_input("")
   else:
      cupcakes -= 1
      print("muffins: {} cupcakes: {}".format(muffins, cupcakes))
      buyItem = raw_input("")

这是一个提前终止的输出示例：

----jGRASP exec: python test.py
m
muffins: 4 cupcakes: 6
m
muffins: 3 cupcakes: 6
m
muffins: 2 cupcakes: 6
c
muffins: 2 cupcakes: 5
c
muffins: 2 cupcakes: 4
c
muffins: 2 cupcakes: 3
m
----jGRASP: operation complete.

但是，如果我输入不同，它工作得很好：

----jGRASP exec: python test.py
m
muffins: 4 cupcakes: 6
m
muffins: 3 cupcakes: 6
m
muffins: 2 cupcakes: 6
m
muffins: 1 cupcakes: 6
m
muffins: 0 cupcakes: 6
m
Out of stock.
c
muffins: 0 cupcakes: 5
c
muffins: 0 cupcakes: 4
c
muffins: 0 cupcakes: 3
c
muffins: 0 cupcakes: 2
c
muffins: 0 cupcakes: 1
c
muffins: 0 cupcakes: 0
c
All out of stock.
----jGRASP: operation complete.

我不确定出了什么问题。想法？

Answer 1

因为一旦离开while "m"，就无法回到那里。

while buyItem == "m":
   #do stuff
while buyItem == "c":
   #do other stuff

#end program

当你输入m -> c -> m，m != c，所以我们离开while buyItem == "c":并结束程序。

我们应该有一个循环，如果我们有库存，则只在最后询问一次输入，否则当完全缺货时退出循环。此外，由于您的作业说仅在输入为0 时才打印：

muffins = 5
cupcakes = 6
buyItem = raw_input("")

while buyItem in ["m", "c", "0"]:
    if buyItem == "m":
        if muffins <= 0:
            print("Out of stock.")
        else:
            muffins -= 1
    elif buyItem == "c":
        if cupcakes <= 0:
            print("Out of stock.")
        else:
            cupcakes -= 1
    elif buyItem == "0":
        print("muffins: {} cupcakes: {}".format(muffins, cupcakes))
        break
    else:  # input is not "m" or "c" or "0"
        print(buyItem.join(" is not a valid input"))
        break

    if muffins <= 0 and cupcakes <= 0:  # we can check this once at the end and break out if we are entirely out of stock
        print("All out of stock.")
        break
    else:  # otherwise, if we have some stock, ask for input
        buyItem = raw_input("")