场景：

web页面如果多人用同一账号同时登录操作，可能会导致数据等的混乱甚至出现故障。并且可能损害开发者的利益。为此，本篇文章就讲下如何实现同一账户同时仅能一个地方登录操作。

思路：

1. 用户登陆时生成token（uuid.uuid4()，保存到数据库并设定session。
2. 用户操作视图加一个装饰器，这个装饰器的功能就是验证session[“token”]和数据库里的token是否一至，不一致的话就返回登录页面，禁止操作

代码：

----app.py
----config.py
----templates (不展示)
----static （不展示）

config.py

import os
from datetime import timedelta
basedir = os.path.abspath(os.path.dirname(__file__))SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:passworld@localhost:3306/singlelogin?charset=utf8'
SQLALCHEMY_TRACK_MODIFICATIONS = False
PERMANENT_SESSION_LIFETIME=timedelta(hours=6)

app.py

from flask import Flask,jsonify,request,redirect,render_template,session
import os
from flask_sqlalchemy import SQLAlchemy
import hashlib
import uuidbasedir = os.path.abspath(os.path.dirname(__file__))
app = Flask(__name__)
app.secret_key = "your secret key"
app.config.from_object("config")
db = SQLAlchemy(app)class User(db.Model):__tablename__ = "users"id = db.Column(db.Integer, primary_key=True)name = db.Column(db.String(64), unique=True)passwd = db.Column(db.String(128))token = db.Column(db.String(128),default=None)def __repr__(self):return self.name
with app.app_context():db.create_all()def loginVaild(fun):def inner(*args, **kwargs):userid=session.get("login_id")session_token=session.get("token")userinfo=User.query.filter_by(id=userid).first()if userinfo.token==session_token:return fun(*args, **kwargs)else:return render_template("login.html")return innerdef setPassword(password):password += "the string you like"md5 = hashlib.md5()md5.update(password.encode())result = md5.hexdigest()return result@app.route("/index",methods=["GET"])
@app.route("/",methods=["GET"])
@loginVaild
def index():print(session)return jsonify(msg="dddd")@app.route("/login",methods=["GET","POST"])
def login():if request.method == "POST":user_name = request.form.get("user_name")user_pwd = request.form.get("user_pwd")if not user_pwd or not user_name:data = "用户名和密码不能为空！"return render_template("login.html", data=data, usr=user_name)login_user = User.query.filter_by(name=user_name).first()if not login_user:data = "用户名不存在！"return render_template("login.html", data=data, usr=user_name)s_pwd = setPassword(user_pwd)if s_pwd != login_user.passwd:data = "密码错误！"return render_template("login.html", data=data, usr=user_name)session["login_name"] = user_namesession["login_id"] = login_user.idnew_token = str(uuid.uuid4())session["token"]=new_tokenlogin_user.token = new_tokendb.session.commit()return redirect("/index")return render_template("login.html")@app.route("/register",methods=["GET","POST"])
def refister():if request.method == "GET":return render_template("register.html")else:user_name = request.form.get("user_name")if User.query.filter_by(name=user_name).first():return jsonify(msg="用户名已存在！")user_pwd = request.form.get("user_pwd")user_pwd = setPassword(user_pwd)user = User(name=user_name, passwd=user_pwd)db.session.add(user)db.session.commit()return jsonify(msg="SUCCESS")if __name__ == '__main__':app.run(host="0.0.0.0",port=8080)