习题 31: 作出决定 · 笨办法学 Python

# 习题 31: 作出决定这本书的上半部分你打印了一些东西，而且调用了函数，不过一切都是直线式进行的。你的脚本从最上面一行开始，一路运行到结束，但其中并没有决定程序流向的分支点。现在你已经学了 if, else, 和 elif ，你就可以开始创建包含条件判断的脚本了。上一个脚本中你写了一系列的简单提问测试。这节的脚本中，你将需要向用户提问，依据用户的答案来做出决定。把脚本写下来，多多鼓捣一阵子，看看它的工作原理是什么。 <table class="highlighttable"><tbody><tr><td class="linenos"> <div class="linenodiv"> <pre> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33</pre> </div> </td> <td class="code"> <div class="highlight"> <pre>print "You enter a dark room with two doors. Do you go through door #1 or door #2?"  door = raw_input("> ")  if door == "1": print "There's a giant bear here eating a cheese cake. What do you do?" print "1. Take the cake." print "2. Scream at the bear."  bear = raw_input("> ")  if bear == "1": print "The bear eats your face off. Good job!" elif bear == "2": print "The bear eats your legs off. Good job!" else: print "Well, doing %s is probably better. Bear runs away." % bear  elif door == "2": print "You stare into the endless abyss at Cthulhu's retina." print "1. Blueberries." print "2. Yellow jacket clothespins." print "3. Understanding revolvers yelling melodies."  insanity = raw_input("> ")  if insanity == "1" or insanity == "2": print "Your body survives powered by a mind of jello. Good job!" else: print "The insanity rots your eyes into a pool of muck. Good job!"  else: print "You stumble around and fall on a knife and die. Good job!" </pre> </div> </td> </tr></tbody></table> 这里的重点是你可以在“if 语句”内部再放一个“if 语句”。这是一个很强大的功能，可以用来创建嵌套(nested)的决定，其中的一个分支将引向另一个分支的子分支。你需要理解 if 语句包含 if 语句的概念。做一下加分习题，这样你会确信自己真正理解了它们。 ### 你应该看到的结果我在玩一个小冒险游戏，我玩的水平不怎么好： ~~~ $ python ex31.py You enter a dark room with two doors. Do you go through door #1 or door #2? > 1 There's a giant bear here eating a cheese cake. What do you do? 1. Take the cake. 2. Scream at the bear. > 2 The bear eats your legs off. Good job! $ python ex31.py You enter a dark room with two doors. Do you go through door #1 or door #2? > 1 There's a giant bear here eating a cheese cake. What do you do? 1. Take the cake. 2. Scream at the bear. > 1 The bear eats your face off. Good job! $ python ex31.py You enter a dark room with two doors. Do you go through door #1 or door #2? > 2 You stare into the endless abyss at Cthuhlu's retina. 1. Blueberries. 2. Yellow jacket clothespins. 3. Understanding revolvers yelling melodies. > 1 Your body survives powered by a mind of jello. Good job! $ python ex31.py You enter a dark room with two doors. Do you go through door #1 or door #2? > 2 You stare into the endless abyss at Cthuhlu's retina. 1. Blueberries. 2. Yellow jacket clothespins. 3. Understanding revolvers yelling melodies. > 3 The insanity rots your eyes into a pool of muck. Good job! $ python ex31.py You enter a dark room with two doors. Do you go through door #1 or door #2? > stuff You stumble around and fall on a knife and die. Good job! $ python ex31.py You enter a dark room with two doors. Do you go through door #1 or door #2? > 1 There's a giant bear here eating a cheese cake. What do you do? 1. Take the cake. 2. Scream at the bear. > apples Well, doing apples is probably better. Bear runs away. ~~~ ### 加分习题为游戏添加新的部分，改变玩家做决定的位置。尽自己的能力扩展这个游戏，不过别把游戏弄得太怪异了。