while循环

第一种用法

#!/usr/bin/python

i = 0
while i < 5 :
    print "i = ", i
    i += 1

i = 0
i = 1
i = 2
i = 3
i = 4

第二种用法

while判断条件:
…
else :
…
当判断条件不满足的时候，执行else后面的表达式

#!/usr/bin/python

i = 0
while i < 10 :
    print "i = ", i
    i += 1
else :
    print "ending ......"

i = 0
i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9
ending ……
有break的情况下

#!/usr/bin/python

while True:
    print "Hello"
    x = raw_input("Please input something:" )
    if x == "q":
        break
else :
    print "ending .........."

Hello
Please input something:1
Hello
Please input something:w
Hello
Please input something:q
如上例子所示，当输入’q’的时候，break执行，跳出循环，但是else下面的表达式不执行。