這次的習題學習的是if/elif/else的用法，另外在附加習題中新增一些判斷條件時，對raw_input的用法更深刻。
首先還是上**（包含附加題中新增的一段）：
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." %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 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"
①if語句的每乙個條件都會進行判斷，在程式執行過程中會對if語句的判斷條件進行遍歷判斷，耗時較多
②if 語句中可以有多個elif的判斷條件，但結尾只有乙個else語句。
③elif後面接判斷條件，else無判斷條件。
④舉個栗子，說明if與elif的區別：
a= true , b = true
if a:
print"a"
if b:
print"b"
這種寫發，輸出的是a和b。
a= true , b = true
if a:
print"a"
elif b:
print"b"
這種寫法，輸出的是a
a= false , b = true
if a:
print"a"
elif b:
print"b"
這種寫法，輸出的是b.
elif的意思是「否則的話，如果……」
2，最後說一下raw_input的部分，在附加題中自己新增的一段**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."
黃色mark部分，前面寫的時候寫成if pray_count == 500:
這個時候不論輸入的是不是500，輸出永遠是：the angle can't decide.後面想到「raw_input() 將所有輸入作為字串看待，返回字串型別」，因此在將500修改為「500」後異常得以解除。
再小的技能都值得認真對待！！！
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