笨办法学python习题31 做出决定

这次的习题学习的是if/elif/else的用法，另外在附加习题中添加一些判断条件时，对raw_input的用法更深刻。

首先还是上代码（包含附加题中新增的一段）：

print"You enter a dark room with two doors. Do you go through door #1 or door #2 or door #3?"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." %bearelif 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 meldies."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!"elif door == "3":print"""There is a angle in front of you,He will help you out.Please pray"""pray_count = raw_input(">")if pray_count == "500":print"The angle help you out,Congratulation!"else:print"The angle can't decide."else:print"You stumble around and fall on a knife and die. Good job"

1，首先说明一下if 和 elif else在使用上的区别：

①if语句的每一个条件都会进行判断，在程序运行过程中会对if语句的判断条件进行遍历判断，耗时较多

②if 语句中可以有多个elif的判断条件，但结尾只有一个else语句。

③elif后面接判断条件，else无判断条件。

④举个栗子，说明if与elif的区别：

a= True , b = True

if a:

print"a"

if b:

print"b"

这种写发，输出的是a和b。

a= True , b = True

if a:

print"a"

elif b:

print"b"

这种写法，输出的是a

a= False , b = True

if a:

print"a"

elif b:

print"b"

这种写法，输出的是b.

elif的意思是“否则的话，如果……”

2，最后说一下raw_input的部分，在附加题中自己新增的一段代码如下：

elif door == "3":print"""There is a angle in front of you,He will help you out.Please pray"""pray_count = raw_input(">")if pray_count == "500":print"The angle help you out,Congratulation!"else:print"The angle can't decide."

黄色mark部分，前面写的时候写成if pray_count == 500:

这个时候不论输入的是不是500，输出永远是：The angle can't decide.后面想到“raw_input() 将所有输入作为字符串看待，返回字符串类型”，因此在将500修改为“500”后异常得以解除。

再小的技能都值得认真对待！！！