習題 31: 作出決定 · 笨辦法學 Python

# 習題 31: 作出決定這本書的上半部分你打印了一些東西，而且調用了函數，不過一切都是直線式進行的。你的腳本從最上面一行開始，一路運行到結束，但其中并沒有決定程序流向的分支點。現在你已經學了 if, else, 和 elif ，你就可以開始創建包含條件判斷的腳本了。上一個腳本中你寫了一系列的簡單提問測試。這節的腳本中，你將需要向用戶提問，依據用戶的答案來做出決定。把腳本寫下來，多多鼓搗一陣子，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> 這里的重點是你可以在“if 語句”內部再放一個“if 語句”。這是一個很強大的功能，可以用來創建嵌套(nested)的決定，其中的一個分支將引向另一個分支的子分支。你需要理解 if 語句包含 if 語句的概念。做一下加分習題，這樣你會確信自己真正理解了它們。 ### 你應該看到的結果我在玩一個小冒險游戲，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. ~~~ ### 加分習題為游戲添加新的部分，改變玩家做決定的位置。盡自己的能力擴展這個游戲，不過別把游戲弄得太怪異了。