while嵌套循环案例

一:使用Python的while嵌套循环打印如下图形:

*
* *
* * *
* * * *
* * * * *

i = 1
while i <= 5:
    j = 1
    str = ''
    while j <= i:
        str = str + '* '
        j += 1
    print(str)
    i += 1

*
* *
* * *
* * * *
* * * * *
* * * *
* * *
* *
*

i = 1
while i <= 5:
    j = 1
    str = ''
    while j <= i:
        str = str + '* '
        j+=1
    print(str)
    i+=1
i = 4
while i>=1:
    j=i
    str = ''
    while(j>=1):
        str = str + "* "
        j-=1
    print(str)
    i-=1

　　总结:之前学的Java,写习惯了,Python有点不习惯,他的代码特别灵活,按行缩进,稍不注意就陷入死循环;但是很好玩;哈哈!

二:Python嵌套循环输出九九乘法表

1*1=1

1*2=2 2*2=4

1*3=3 2*3=6 3*3=9

1*4=4 2*4=8 3*4=12 4*4=16

1*5=5 2*5=10 3*5=15 4*5=20 5*5=25

1*6=6 2*6=12 3*6=18 4*6=24 5*6=30 6*6=36

1*7=7 2*7=14 3*7=21 4*7=28 5*7=35 6*7=42 7*7=49

1*8=8 2*8=16 3*8=24 4*8=32 5*8=40 6*8=48 7*8=56 8*8=64

1*9=9 2*9=18 3*9=27 4*9=36 5*9=45 6*9=54 7*9=63 8*9=72 9*9=81

i = 1
while i <= 9:
    j = 1
    while j <= i:
        print("%d*%d=%-2d"%(j,i,j * i), end=' ')
        j += 1
    print("
")
    i += 1

 三:实现简单的用户登录控制

i =0
userName = 'Python'
userPassword = '123456'
while i<3:
    name = input("请输入用户名:")
    password = input("请输入密码:")
    if(name==userName and password==userPassword):
        print("登陆成功!")
        break
    elif(name==userName):
        print("密码有误,请重新输入!")
    elif(password == userPassword):
        print("用户名输入有误,请重新输入!")
    else:
        print("用户名和密码错误!")
    i+=1;
    print("温馨提示:您还有%d次登录机会"%(3-i))
print("今天登陆次数已达上限,今晚想想;明天再来哈!")