Loops

For-loops：
For-loops 的两种方式：

1. the_count = [1, 2, 3, 4, 5]

   for number in the_count:

    print "This is count %d" % number

   输出结果为：

   This is count 1

   This is count 2

   This is count 3

   This is count 4

   This is count 5 

2. for i in range(0, 6):

    print i

   输出结果为：

   0

   1

   2

   3

   4

   5

   注意6是不执行的，也就是说是0 <= i < 6

while-loops:
A while-loop will keep executing the code block under it as long as a boolean expression is True.
Example:
i = 0
numbers = []

while i < 6:
    print "At the top i is %d" % i
    numbers.append(i)

    i = i + 1
    print "Numbers now: ", numbers
    print "At the bottom i is %d" % i


print "The numbers: "

for num in numbers:
    print num

中途退出（适用于循环或判断）：
exit(0)
但是使用之前要加上from sys import exit