序列
listnameandpin = [
['kai','123'],
['je','456'],
['eejun','789'],
['jieang','234'],
['yangzi','678'],
]
username = raw_input('please inter your username:')
password = raw_input('plaese inter your password:')
if [username,password] in listnameandpin:
print "check ok"
else:
print "check error,please inter again"
#第一次练习出现2个错误；
#问题1：在设置变量名称时，没有在列表之间加挂号；
#问题2：在if函数后面的列表中，增加了‘’；