{% block body %} {% if session['logged_in'] %} You're logged in already! {% else %} <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=0.5, maximum-scale=3.0, user-scalable=yes" /> <form action="/login" method="POST"> <p><input type="username" name="username" placeholder="邮箱地址、电话号码"></p> <p><input type="password" name="password" placeholder="密码"></p> <p><input type="submit" value="登录"></p> </form> {% endif %} {% endblock %}