1.##发生了什么：
我有一个HTML代码，它向flask代码发送POST请求。这是一个登录页面。（我使用SQLite3和Flask。）
1.##HTML代码：

<div class="col">
            <div class="login-box">
            <h2>Register</h2>
            <form method="post" action="{{ url_for('register_post') }}">
                <div class="user-box">
                    <input type="email" name="email" placeholder="Email Address" required>
                </div>
                <div class="user-box">
                    <input type="password" name="password" placeholder="Password" required>
                </div>
                <div class="user-box">
                    <input type="text" name="username" placeholder="Username" required>
                </div>
                <div class="button-form">        
                    <a id="submit" href="{{url_for('register_post')}}">Submit</a>
                    <div id="register">
                        Already Have An Account ?
                        <a href="{{url_for('login')}}">Login Now !</a>
                    </div>
                </div>
            </form>
        </div>
    </div>

1.##Python代码：

@app.route('/register', methods=['POST'])
def register_post():
    print("Got a data")
    username = request.form['username']
    email = request.form['email']
    password = request.form['password']
    c.execute('''INSERT INTO users (email, username, password) VALUES (?,?,?)''', (email, username, password))
    conn.commit()
    conn.close()

    return redirect(url_for('login'))

没有traceback，这（可能）意味着函数甚至没有被调用。