pip3.6 install flask-login

from flask.ext.login import LoginManager

......

login_manager=LoginManager()
login_manager.session_protection="strong" 

#可设置为None，basic，strong已提供不同的安全等级
login_manager.login_view="login" #设置登录页

from flask.ext.login import UserMixin

class User(UserMixin,db.Model):
  __tablename__="users"
  id=db.Column(db.Integer,primary_key=True)
  ......
  

@login_manager.user_loader
def load_user(user_id):
  return User.query.get(int(user_id))

{%extends "bootstrap/base.html "%}
{% block title%}牛博客 {% endblock %}<!--覆盖title标签-->

{% block navbar %}
<nav class="navbar navbar-inverse"><!-- 导航部分 -->
 <div class="navbar-header">
   <a class="navbar-brand" href="#" rel="external nofollow" rel="external nofollow" >
    牛博客
   </a>
 </div>

 <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
   <ul class="nav navbar-nav">
    <li><a href="/" rel="external nofollow" >首页</a></li>
   </ul>
   <ul class="nav navbar-nav navbar-right">
    {% if current_user.is_authenticated %}
      <li><p class="navbar-text"><a href="#" rel="external nofollow" rel="external nofollow" class="navbar-link">{{current_user.username}}</a> 您好</p></li>
      <li><a href="{{url_for('logout')}}" rel="external nofollow" >登出</a></li>
    {% else %}
      <li><a href="{{url_for('login')}}" rel="external nofollow" >登录</a></li>
    {% endif %}
   </ul>
  </div><!-- /.navbar-collapse -->
</nav>
{% endblock %}
{% block content %} <!--具体内容-->
<div class="container">
</div>
{% endblock %}

class LoginForm(Form):
  username=StringField("请输入用户名",validators=[DataRequired()])
  password=PasswordField("请输入密码")
  remember_me=BooleanField("记住我")
  submit=SubmitField("登录")

@app.route("/login",methods=["GET","POST"])
def login():
  form=LoginForm()
  if form.validate_on_submit():
    username = form.username.data
    password = form.password.data
    user = User.query.filter_by(username=username, password=password).first()
    if user is not None:
      login_user(user,form.remember_me.data)
      return redirect(url_for("index"))
    else:
      flash("您输入的用户名或密码错误")
      return render_template("/login.html",form=form) # 返回的仍为登录页
  return render_template("/login.html",form=form)

@app.route("/logout",methods=["GET","POST"])
@login_required
def logout():
  logout_user()
  return redirect(url_for("index"))