while小用

1.使用while打印1 2 3 4 5 6 8 9 10

#!/usr/bin/env python
#encoding: utf-8
num = 1
while num < 11:
    if num == 7:
        print
    else:
        print num
    num = num + 1

执行结果：

[root@localhost zuoye]# python 1.py 
1
2
3
4
5
6

8
9
10

2.求1到100的和

#!/usr/bin/env python
#encoding: utf-8
num = 1
sum = 0
flag = True
while flag:
    sum = sum + num
    if num == 100:
        flag = False
        print sum
    num = num + 1

执行结果：

[root@localhost zuoye]# python 2.py 
5050

3.求1到100奇数的和

#!/usr/bin/env python
#encoding: utf-8
num = 1
sum = 0
flag = True
while flag:
    sum = sum + num
    if num == 99:
        flag = False
        print sum
    num = num + 2

执行结果：

[root@localhost zuoye]# python 3.py 
2500

4.求1到100偶数的和

#!/usr/bin/env python
#encoding: utf-8
num = 2
sum = 0
flag = True
while flag:
    sum = sum + num
    if num == 100:
        flag = False
        print sum
    num = num + 2

执行结果：

[root@localhost zuoye]# python 4.py 
2550

5.求和1-2+3-4......+99-100

#!/usr/bin/env python
#encoding: utf-8
num = 1
sum = 0
flag = True
while flag:
    if num%2 == 1:
        sum = sum + num
        if num == 99:
            flag = False
            print sum
    else:
        sum = sum - num
    num = num + 1

执行结果：

[root@localhost zuoye]# python 5.py 
50

6.用户登录，三次机会重试

#!/usr/bin/env python
#encoding: utf-8
flag = True
num = 1
while flag:
    Name = raw_input('please enter you name: ')
    Passwd = int(raw_input('please enter you passwd: '))
    if Name == "kebi" and Passwd == 123:
        print "密码正确"
        flag = False
    else:
        num = num + 1
        if num == 4:
            flag = False
            print "对不起，已经三次输入错误。"

执行结果：

一次答对：
[root@localhost zuoye]# python 6.py 
please enter you name: kebi
please enter you passwd: 123
密码正确

两次答对：

[root@localhost zuoye]# python 6.py 
please enter you name: 4356
please enter you passwd: 3456
please enter you name: kebi
please enter you passwd: 123
密码正确

三次达错：
[root@localhost zuoye]# python 6.py
please enter you name: 123
please enter you passwd: 123
please enter you name: 123
please enter you passwd: 123
please enter you name: 123
please enter you passwd: 123
对不起，已经三次输入错误。