用户登录（三次机会）

i = 3
username = 'zhourui'
password = 123
while i>0:
    i -= 1
    name = input('请输入用户名：')
    while name == username:
        word = int(input('请输入密码：'))
        if word == password:
            print('登陆成功')
            break
        else:
            print('密码错误，你还有'+str(i)+'次机会')
            if i == 0:
                print('机会用完，登陆失败')
                ask = input('再试试？Y')
                if ask == 'Y':
                    i = 2
                    continue
                break
            i -= 1
            continue
    break
    if name != username:
        print('用户名错误，你还有'+str(i)+'次机会')
        if i == 0:
            print('机会用完，登陆失败')
            ask = input('再试试？Y')
            if ask == 'Y':
                i = 2
                continue
            break