while循环
（一）菠菜平台修复【企 娥:217 1793 408】
while 后面接判断语句，在返回结果时有以下几种语句：
1、break
仅适用于循环语句，意思是结束最近的循环
2、continue
仅适用于循环语句，意思是跳到最近的循环首行
3、pass
空占位语句
4、else
不满足循环的判断条件时执行同级别的else语句
可通过执行一下猜错语句感受break与continue的区别
_uesr = 'yangdanhua'
_password = '123456'
count = 0
while True:
user = input('username:')
password = input('password:')
if user == _uesr and password == _password:
print ('welcome to {my} world'.format(my = user) )
break
else:
print ('Invaild')
count +=1
if count == 3:
count_panduan = input('Do you want to try again? (N/Y)')
if count_panduan == 'y':
count = 0
continue
else:
print ('see you')
break
pass与else详见：
a = input('please input num1:')
b = input('please input num2')
while a>b:
pass #不输出任何内容
else:
print ('can not meet the condition')