完成注册功能

import config
from flask import Flask,render_template,request,redirect,url_for,session
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config.from_object(config)
db = SQLAlchemy(app)

#创建用户模型
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(20),nullable=False)

#db.create_all()


@app.route(‘/‘)
def first():
    return render_template(‘first.html‘)

@app.route(‘/sign_up/‘,methods=[‘GET‘,‘POST‘])#登录
def sign_up():
    return render_template(‘sign_up.html‘)

@app.route(‘/sign_in/‘,methods=[‘GET‘,‘POST‘])#注册
def sign_in():
    if request.method == "GET":
        return render_template("sign_in.html")
    else:
        username = request.form.get("username")
        password = request.form.get("password")
        user = User.query.filter(User.username == username).first()
        if user:
            return ‘username existed.‘
        else:
            user = User(username=username, password=password)
            db.session.add(user)
            db.session.commit()
            return redirect(url_for(‘sign_up‘))


@app.route(‘/chat/‘)
def chat():
    return render_template(‘chat.html‘)


if __name__ == ‘__main__‘:
    app.run(debug=True)

{% extends ‘first.html‘%}
{% block title %}
注册*
{% endblock %}
{% block head %}
    <link href="{{ url_for(‘static‘,filename=‘css/sign.css‘) }}" rel="stylesheet" type="text/css">
    <script src="{{ url_for(‘static‘,filename=‘js/sign.js‘) }}"></script>
{% endblock %}


{% block main %}
    <div class="box">
        <h3>欢迎注册</h3>
        <form action="{{ url_for("sign_in") }}" method="post">
            <div class="input_box">
               输入用户名： <input id="uname"  name="username" type="text" placeholder="请输入用户名" class="b1">
        </div>
             <div class="input_box">
                输入密码： <input id="upass" name="password" type="password" placeholder="请输入密码" class="b1">
             </div>
            <div class="input_box">
                确认密码： <input id="checkpass" name="passnameagain" type="password" placeholder="请确认密码" class="b1">
             </div>
        <div id="error_box" class="error_box"><br></div>
        <div class="button">
            <button  class="login" onclick="fnLogin()">登录</button>
            <button  class="cancel" onclick=window.alert("是否确认离开，您输入的数据可能不会被保存")>取消</button></div>
    </div>
{% endblock %}

function fnLogin() {
    var oUname=document.getElementById("uname");
    var oUpass=document.getElementById("upass");
    var oError=document.getElementById("error_box");
    var oCheckpass = document.getElementById("checkpass");
    var isError = true;
    oError.innerHTML="<br>";
    if(oUname.value.length<6||oUname.value.length>12){
        oError.innerHTML="用户名的长度需为6-20位";
        isError = false;
        return;
    }else if((oUname.value.charCodeAt(0)>=48)&&(oUname.value.charCodeAt(0)<=57)){
        oError.innerHTML="首字母不能是数字。";
        isError = false;
        return;
    }else for(var i=0;i<oUname.value.length;i++){
        if((oUname.value.charCodeAt(i)<48||oUname.value.charCodeAt(i)>57)&&(oUname.value.charCodeAt(i)<97||oUname.value.charCodeAt(i)>122)){
            oError.innerHTML="只能包含字母或数字。";
            isError = false;
            return;
        }
    }
    if (oUpass.value.length<6||oUpass.value.length>12){
        oError.innerHTML="密码的长度需为6-20位";
        isError = false;
        return;
    }
    if(oCheckpass.value!=oUpass.value){
        oError.innerHTML="输入密码不一致。";
        isError = false;
        return;
    }else if(oCheckpass.value==""){
        oError.innerHTML="未确认密码。";
        isError = false;
        return;
    }
    return isError;
    window.alert("登录成功！")
}