Question

我正在研究MyProgrammingLab问题，该问题说明如下：

你在一家出售两种食品的面包店工作：松饼和蛋糕。在任何给定时间，您店内的松饼和蛋糕的数量都存储在为您定义的变量松饼和蛋糕中。   编写一个程序，从标准输入中获取字符串，表明客户正在购买的产品（＆＃34;松饼＆＃34;用于松饼，＆＃34;蛋糕＆＃34;用于蛋糕）。如果他们买松饼，减少一个松饼，如果他们买了一个蛋糕，减少一个蛋糕。如果没有更多的烘焙食品，请打印（＆＃34;缺货＆＃34;）。

一旦你完成销售，输入＆＃34; 0＆＃34;，然后让程序打印出剩余的松饼和蛋糕的数量，形式为＃34;松饼：9个蛋糕：3＆＃34; （例如，如果剩下9个松饼和3个蛋糕）。

我在jGRASP中测试我的代码（不是一个粉丝，不幸的是课程需要）并且该程序按预期工作，但它似乎有时会提前终止，我正在努力找出原因，因为我在我的逻辑中找不到任何错误。这就是我所拥有的：

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("")

这是一个早期终止的输出示例：

----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，如果我输入的方式不同，它可以正常工作：

----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.

我不确定是什么错。想法？

Answer 1

因为一旦你离开while "m"，你就无法回到那里。

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

#end program

当您输入m -> c -> m，m != c时，我们离开while buyItem == "c":并结束该计划。

我们应该有一个循环，并且如果我们有库存则只在最后请求输入一次，否则在完全缺货时突破循环。此外，由于您的作业仅表示输入为0时打印：

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("")

程序提前结束的时间比我预期的要早

1 个答案: