ex29~ex32有关分支、列表和循环

分支就是分叉，由一个点来发散，发散成两条线以上，编程语句用if-elif-if和逻辑表达式，这个逻辑表达式就是前面所说的布尔运算，得出的结果就是“真”或“假”，以此为依据来决定是否执行冒号后面的代码块，好的，终于描述清楚了，摘选这几课中比较有用的代码贴上来

ex30

# coding=utf-8
people = 30
cars = 40
trucks = 15

if cars > people:
    print "We should take the cars."
elif cars < people:
    print "We should not take the cars."
else:
    print "We can't decide."

if trucks > cars:
    print "That's too many trucks."
elif trucks < cars:
    print "Maybe we could take the trucks."
else:
    print "We still can't decide."

if people > trucks:
    print "Alright, let's just take the trucks."
else:
    print "Fine, let's stay home then."

ex31

# coding=utf-8

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 abyes 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 "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!"

ex32

# coding = utf-8
the_count = [1,2,3,4,5]
fruits =['apples','oranges','pears','apricots']
change = [1,'pennies',2,'dimes',3,'quarters']

for number in the_count:
    print "This is count %d" % number

for fruit in fruits:
    print "A fruit of type: %s" % fruit

for i in change:
    print "I got %r" % i 

elements = []

for i in range(0,6):
    print "Adding %d to the list." % i 
    elements.append(i)

for i in elements:
    print "Element was : %d" % i 

在后续的程序中，for与列表有大量的配合使用

说一下range()函数，这个函数也是会在后面大量的使用，整理一下它的几个点：

• range(1,5)输出的结果是[1, 2, 3, 4]记住是没有5的
• range(5) 输出的结果是[0,1, 2, 3, 4]记住是从0开始的
• range(0,5,2)输出的结果是[0,2,4],输出的顺序是0，加2，加2，最大值要小于5

列表的相关的操作，现有列表list = [1, 2, 3, 4, 5]

• list[0:]列出0号（包括0）以后的内容，结果是[1,2,3,4,5]
• list[1:]列出1号（包括1）以后的内容，结果是[2,3,4,5]
• list[:-1]列出-1号之前的（这里不包括-1号）结果是[1,2,3,4]
• list[2:-2]结果是[3]
• list[::]与list[:]效果一样都是显示全部
• list[::2]结果是[1,3,5]
• list[2::]结果是[3,4,5]
• list[::-1]结果是[5,4,3,2,1]
• list[::-2]结果是[5,3,1]

append()函数就是给list在最后面添加数据，例如:
list.append('haha'),那么上面的列表内容就是[1, 2, 3, 4, 5，‘haha'],网上搜了一下，还有个相似的函数，扩展一下extend():
list.extend(['haha','lulu'])结果是list = [1, 2, 3, 4, 5,'haha','lulu']