Learn Python The Hard Way学习(31) - 做出选择

在以前的练习中，我们一直在打印和调用函数，所有的程序都是至上而下执行的。如果你写了一个函数，执行的时候需要你自己选择执行哪个分支，现在我们就可以用if，else和elif实现这。

上一个练习只是一些简单的问答集，下面的练习我们提出问题，并且由用户自己选择答案。

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 id 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 survies 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!"

这么代码的重点是if语句里面包含if语句，这种嵌套非常的强大和常用。

运行结果

root@he-desktop:~/mystuff# 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!
root@he-desktop:~/mystuff# 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 Cthulhu's retina.
1. Blueberries.
2. Yellow jacket clothespins.
3. Understanding revolvers yelling melodies.
> 1
Your body survies powered by a mind of jello. Good job!
root@he-desktop:~/mystuff#

加分练习
扩展上面的游戏，添加一些新的判断。