class User(db.Model):    __tablename__ = 'user'    id = db.Column(db.Integer, primary_key=True, autoincrement=True)    username = db.Column(db.String(20), nullable=False)    _password = db.Column(db.String(200), nullable=False)#内部使用    nickname = db.Column(db.String(20))    @property    def password(self):  # 外部使用        return self._password    @password.setter    def password(self, row_password):#定义属性        self._password = generate_password_hash(row_password)    def check_password(self,row_password):        result = check_password_hash(self._password,row_password)#检查密码        return result复制代码复制代码@app.route('/login/', methods=['GET', 'POST'])def login():    if request.method == 'GET':        return render_template("login.html")    else:        usern = request.form.get('username')        password1 = request.form.get('password')        user = User.query.filter(User.username == usern).first()        if user:            if user.check_password(password1):                session['user'] = usern                session['id'] = user.id                session.permanent = True                return redirect(url_for('index'))            else:                return '密码错误'        else:            return '用户名不存在'