python要开始记录了20181125

 print('1、使用while循环输入 1 2 3 4 5 6     8 9 10')
 i = 1
 while i < 10:
     i += 1
     if i == 7:
          continue       #print(' ')这两个可以替换一下，看看不同的效果
     else:
         print(i)

 print('2、求1-100的所有数的和')
 i = 0
 sum = 0
 while i < 100:
       i += 1
       sum = sum + i
       print(sum)

 print('3、输出 1-100 内的所有奇数')
 i = 0
 while i < 100:
     i += 1
     if i %2 != 0:
         print(i)

 print('4、输出 1-100 内的所有偶数')
 i = 0
 while i < 100:
     i += 1
     if i %2 == 0:
         print(i)

 print('5、求1-2+3-4+5 ... 99的所有数的和')
 i = 0
 sum = 0
 j = -1
 while i < 99:
     i += 1
     if i %2 != 0:
         sum = sum + (i * (-j))
     if i %2 == 0:
         sum = sum + (i * j)
 print(sum)

 print('6、用户登陆（三次机会重试）')
 i = 0
 name = 'allison'
 password = ''
 while i < 3:
     na = input('请输入用户名：')
     pw = input('请输入密码：')
     i += 1
     oppo = 3 - i
     if na == name and pw == password:
         print('输入正确')
         break
     elif na != name or pw != password:
         print('输入错误， 还有%d次机会'%(oppo))
         if i == 3:
             answer = input('输入Y再试试？')
             if answer == 'Y':
                 print('再来三次机会')
                 i = 0
             else:
                 print('机会已用完')