用户登陆三次机会

li = [{'username':'alex','password':'123'},
    {'username':'wusir','password':'23'},
    {'username':'taibai','password':'34'},
      ]
j = 0
while j < 3 :
    username = input('姓名：')
    password = input('密码：')
    for i in li :
        if username == i['username'] and password == i['password']:
            print('登陆成功！')
            j=3
            break
    else:
        print('登陆不成功，请重新输入~')
        if j == 2:
            choice = input('是否再试试？Y')
            if choice=='Y':
                j=-1
    j=j+1