没有 for 或 while 循环的字典递归

Question

我对 python 相当陌生，我已经被你们中的许多人认为是小菜一碟的挑战。输出必须是：The Monkey-child could not fall asleep, so the mother told him a story, he was once a Tiger-child  The Tiger-child could not fall asleep, so the mother told him a story, he was once a Human-child    The Human-child could not fall asleep, so the mother told him a story, he was once a Panther-child      The Panther-child could not fall asleep, so the mother told him a story, he was once a Snake-child      The Snake-child has tired and fell asleep     The Panther-child has tired and fell asleep    The Human-child has tired and fell asleep   The Tiger-child has tired and fell asleep  The Monkey-child has tired and fell asleep修改代码是以下（for和while循环是不允许的）： import sys StorySequence = {     "Monkey": "Tiger",     "Tiger": "Human",     "Panther": "Snake",     "Snake": "",     "Human": "Panther" } def writePaddingForDepth(depth):     for i in range(0, depth):         sys.stdout.write('  ')         sys.stdout.flush() def endStory(thread, depth):     writePaddingForDepth(depth)     print ("The " + thread + "-child has tired and fell asleep.")     return True def startStory(thread, depth):    if (len(StorySequence[thread]) == 0):        return endStory(thread, depth) writePaddingForDepth(depth) print ("The " + thread + "-child could not fall asleep, "        "so the mother told him a story, he was once "        + StorySequence[thread] + "-child") ## Code here startStory("Monkey", 0)我试图处理它就像它是 C 中的数组一样，但显然它不是，据我所知，它是一种dict类型，这对我来说是全新的。我想知道如何在这个例子中实现没有for或while循环的递归。

Answer 1

而不是做

for i in range(0, depth):

 sys.stdout.write('  ')

打印两倍的空格数depth，你可以这样做

sys.stdout.write('  ' * depth)

你可以做类似的事情

def fn(who, depth):

  if(who in StorySequence):

    if(StorySequence[who]!=''):

      print ("\t" * depth + "The " + who + "-child could not fall asleep, "

          "so the mother told him a story, he was once "

          + StorySequence[who] + "-child")

      fn(StorySequence[who], depth+1)

    print ("\t" * depth + "The " + who + "-child has tired and fell asleep.")

fn("Monkey", 0)

递归函数必须有一个退出条件，以防止它成为无限递归。

在这里，只要字典中有一个有效的键并且值不是空字符串，递归就会完成。

who in StorySequence用于检查who字典中是否存在内容为 的键StorySequence。