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python 循环 while

死循环

1 2	`while` `1` `==` `1:` 　　`print("ok")`

import  datetime
while 1 == 1:
    print("ok",datetime.datetime.now())

指定循环条件退出

1 import  datetime
2 count = 0
3 while  count < 10:
4     print("ok",datetime.datetime.now())
5     count = 100
6 print('123')

指定循环条件大于退出

1 import  datetime
2 count = 0
3 while  count <= 10:
4     print("ok",datetime.datetime.now(),count)
5     count = count +1
6 print('123')

练习题

使用while循环输入 1 2 3 4 5 6 8 9 10

import  datetime
while True:
    count = int(input("请输入数字:"))
    if count == 7:
        continue
    elif count > 10:
        exit()
    print(datetime.datetime.now(),count

求1-100的所有数的和

import  datetime
number =  list(range(1,100))
sum = 0
for i in number:
    sum = sum + i
    print(i,datetime.datetime.now())
print(sum)

输出 1-100 内的所有奇数

import  datetime
number =  list(range(1,100))
for i in  number:
    if  i%2 != 0:
        print(i,datetime.datetime.now())

输出 1-100 内的所有偶数

import  datetime
number =  list(range(1,100))
for i in  number:
    if  i%2 == 0:
        print(i,datetime.datetime.now())

求1-2+3-4+5 ... 99的所有数的和

import  datetime
number =  list(range(1,100))
sum1 = 0
sum2 = 0
for i in  number:
    if i%2 != 0:
        sum1= sum1 + i
        print(sum1,datetime.datetime.now(),'奇数')
    else:
        sum2 = sum2 + i
        print(sum2,datetime.datetime.now(),'偶数')
sum = sum2 + sum1
print(sum)

 1 n = 1
 2 s = 0  # s是之前所有数的总和
 3 while n < 100:
 4     temp = n % 2
 5     if temp == 0:
 6         s = s - n
 7     else:
 8         s = s + n
 9     n = n + 1
10 print(s)

用户登陆（三次机会重试）

num = 1
while True:
    a = input("UserName:")
    b = input("PassWord:")
    if a == "zzq" and b == "wyzzq8023":
        print (u"登录成功...")
        break
    elif num > 3:
        print (u"用户名或密码错误...")
        print (u"输入次数达到上限，退出程序...")
        break
    else:
        print (u"用户名或密码错误，请重新输入...")
        num += 1
        continue