Detailed example of recording user account login status (python)

The birth of a flask-based web application is the sixth article. This article mainly introduces the development of the function of recording user account login status. It has certain reference value. Interested friends can refer to the previous

The login and registration functions have been completed, but after logging in successfully and returning to the homepage, I found that it is still completely white. Yes, the title has always been written on the blog, so the ultimate goal is to write a light blog, but before publishing the article, is it right? Do you want to record the login status first?

User login

There are many ways to record login status. The first thing that comes to mind is to use the session that comes with flask, but flask also provides a A more convenient extension, the flask-login package, can be used in the same way as before. You first need to install it:

pip3.6 install flask-login

and then initialize it in default.py:

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

and then modify it according to your needs. The User model is modified because Flask-Login requires that the User model must implement four methods, which are:

is_authenticated() Determine whether to log in, log in and return True, otherwise return False
is_active() Whether login is allowed, that is, whether the user has been disabled, if disabled, return False
is_anonymous() Falsefor ordinary users
get_id() Return the user's unique identifier, using Unicode encoding

These four methods can be implemented directly in the User model, but there is a simpler way, which is to inherit the UserMixin class provided by Flask-Login, which It contains the default implementation of these methods. The modified User model is:

from flask.ext.login import UserMixin

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

flask-login also requires the program to implement a callback function, and the specified identifier is used in the user:

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

After that, you can easily use the flask-login framework and continue to modify the navigation part of the homepage template to display the user name and corresponding information:

{%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 -->
 <p class="navbar-header">
   <a class="navbar-brand" href="#" rel="external nofollow" rel="external nofollow" >
    牛博客
   </a>
 </p>

 <p 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(&#39;logout&#39;)}}" rel="external nofollow" >登出</a></li>
    {% else %}
      <li><a href="{{url_for(&#39;login&#39;)}}" rel="external nofollow" >登录</a></li>
    {% endif %}
   </ul>
  </p><!-- /.navbar-collapse -->
</nav>
{% endblock %}
{% block content %} <!--具体内容-->
<p class="container">
</p>
{% endblock %}

The url_for method appears here, and its main function is to use the program Generate a URL based on the information, such as passing in the method name of the view to generate the corresponding URL. You can also generate URL parameters through the dynamic parameters of the method, such as url_for('index',age=5), the result is /?age=5

The main content is to determine whether you are logged in. If you are logged in, it will display {{username}} Hello and provide a logout function. Otherwise, the login link will be displayed.

Modify login form:

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")

Add remember me item, BooleanField defaults to multi-select button

Modify login view method:

@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)

where login_user is The flask_login plug-in is provided to set user login. The second parameter is the remember me option. If True is entered, the cookie storage status is provided. Otherwise, closing the browser status will cancel it.

New logout method ：

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

This method is very simple. Just use the logout method provided by flask-login. Note that the @login_required decorator indicates that only logged-in users can access this view method.

Run the test and enter the home page address:

Click the login button in the upper right corner:

Enter user name zhangji password 123 and select remember me, click OK:

Pay attention to the red line part, the display is normal, click to log out at this time:

Pay attention to the red line and return to the initial state.

Chapter Conclusion

The next step was supposed to be the post and follow functions, but it is obvious that the code is now in default.py, and the code structure is becoming increasingly difficult to handle. , so the length of this chapter is relatively small. The next chapter will focus on refactoring the existing code and grouping the functions, and then continue to write the next functions. Thanks for watching.

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