python 分支和函數(shù)

練習35.分支和函數(shù)

你已經(jīng)學會了 if 語句、函數(shù)、還有列表?，F(xiàn)在你要練習扭轉一下思維了。把下面的代碼寫下來，看你是否能弄懂它實現(xiàn)的是什么功能。

from sys import exit

def gold_room():
    print "This room is full of gold.  How much do you take?"

    choice = raw_input("> ")
    if "0" in choice or "1" in choice:
        how_much = int(choice)
    else:
        dead("Man, learn to type a number.")

    if how_much < 50:
        print "Nice, you're not greedy, you win!"
        exit(0)
    else:
        dead("You greedy bastard!")

def bear_room():
    print "There is a bear here."
    print "The bear has a bunch of honey."
    print "The fat bear is in front of another door."
    print "How are you going to move the bear?"
    bear_moved = False

    while True:
        choice = raw_input("> ")

        if choice == "take honey":
            dead("The bear looks at you then slaps your face off.")
        elif choice == "taunt bear" and not bear_moved:
            print "The bear has moved from the door. You can go through it now."
            bear_moved = True
        elif choice == "taunt bear" and bear_moved:
            dead("The bear gets pissed off and chews your leg off.")
        elif choice == "open door" and bear_moved:
            gold_room()
        else:
            print "I got no idea what that means."

def cthulhu_room():
    print "Here you see the great evil Cthulhu."
    print "He, it, whatever stares at you and you go insane."
    print "Do you flee for your life or eat your head?"

    choice = raw_input("> ")

    if "flee" in choice:
        start()
    elif "head" in choice:
        dead("Well that was tasty!")
    else:
        cthulhu_room()

def dead(why):
    print why, "Good job!"
    exit(0)

def start():
    print "You are in a dark room."
    print "There is a door to your right and left."
    print "Which one do you take?"

    choice = raw_input("> ")

    if choice == "left":
        bear_room()
    elif choice == "right":
        cthulhu_room()
    else:
        dead("You stumble around the room until you starve.")

start()

你看到的結果

這是我玩這個游戲的過程：

$ python ex35.py
You are in a dark room.
There is a door to your right and left.
Which one do you take?
>  left
There is a bear here.
The bear has a bunch of honey.
The fat bear is in front of another door.
How are you going to move the bear?
>  taunt bear
The bear has moved from the door. You can go through it now.
>  open door
This room is full of gold.  How much do you take?
>  1000
You greedy bastard! Good job!

附加題

1. 把這個游戲的地圖畫出來，把自己的路線也畫出來。
2. 改正你所有的錯誤，包括拼寫錯誤。
3. 為你不懂的函數(shù)寫注釋。
4. 為游戲添加更多元素。通過怎樣的方式可以簡化并且擴展游戲的功能呢？
5. 這個gold_room游戲使用了奇怪的方式讓你鍵入數(shù)字。這種方式會導致什么樣的 bug？ 你可以用比檢查0、1更好的方式判斷輸入是否是數(shù)字嗎？int() 這個函數(shù)可以給你一些頭緒。

常見問題

Q: 求助！這個程序是怎樣運行的？

當你理解一段代碼遇到困難的時候，可以給每一行代碼加上一段簡單的注釋用來解釋每一句實現(xiàn)什么功能。盡量使你的注釋短小且與代碼近似.然后用圖解或者寫一段描述來弄懂代碼是如何工作的。如果你這么做了，你就能弄明白這段代碼是如何工作的。

Q: 你為什么用了while True?

這么寫可以創(chuàng)建一個無限循環(huán)

Q: exit()是干什么的？

在許多操作系統(tǒng)中可以使用exit(0)來中止程序，傳遞的數(shù)字參數(shù)表示是否遇到異常。如果使用exit(1)退出將會出現(xiàn)一個錯誤，但是用exit(0)就是正常的退出。參數(shù)部分和正常的布爾邏輯正好是相反的 (正常的布爾邏輯中 0==False) 您可以使用不同的數(shù)字來表示不同的錯誤結果。你也可以用exit(100)來表示一個不同于exit(2)和 exit(1)的錯誤信息.

Q: 為什么有時候把raw_input 寫成raw_input('>')

raw_input的參數(shù)只是一個字符串，會打印顯示在要求用戶輸入之前。