完成登录功能，用session记住用户名

登录功能完成：

1. js:设置return
2. html:设置
   1. form
   2. input
3. py:
   1. @app.route设置methods
   2. GET
   3. POST
      1. 读取表单数据
      2. 查询数据库
         1. 用户名密码对：
            1. 记住用户名
            2. 跳转到首页
         2. 用户名密码不对：
            1. 提示相应错误。

session：

1. 从`flask`中导入`session`
2. 设置`SECRET_KEY`
3. 操作字典一样操作`session`：增加用户名`session['username']=`username

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

import config

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


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)
    nickname = db.Column(db.String(20))


db.create_all()


# 增加
# user = User(username='tan1997',password='19961021')
# db.session.add(user)
# db.session.commit()

# 查询
# user = User.query.filter(User.username == 'tan1997').first()
# print(user.username,user.password)

# 修改
# user=User.query.filter(User.username == 'tan1997').first()
# user.password=1234567
# db.session.commit()

# 删除
# user=User.query.filter(User.username == 'tan1997').first()
# db.session.delete(user)
# db.session.commit()

@app.route('/')
def myweb():
    return render_template("myweb.html")


@app.route('/login/', methods=['GET', 'POST'])
def login():
    if request.method == 'GET':
        return render_template("login.html")
    else:
        username = request.form.get('username')
        password = request.form.get('password')
        user = User.query.filter(User.username == username).first()
        if user:
            if user.password == password:
                return redirect(url_for('myweb'))
            else:
                return '密码错误'
        else:
            return '用户名不存在'



@app.route('/regist/', methods=['GET', 'POST'])
def regist():
    if request.method == 'GET':
        return render_template("regist.html")
    else:
        username = request.form.get('username')
        password = request.form.get('password')
        nickname = request.form.get('nickname')
        user = User.query.filter(User.username == username).first()
        if user:
            return ' 用户名已存在'
        else:
            user = User(username=username, password=password, nickname=nickname)
            db.session.add(user)  # 数据库，添加操作
            db.session.commit()
            return redirect(url_for('login'))


@app.route('/question/')
def question():
    return render_template("question.html")


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

{% extends'myweb.html' %}
{% block logintitle %}登录页面{% endblock %}


{% block loginhead %}
    <link rel="stylesheet" type="text/css" href="../static/css/component.css"/>
    <script src="../static/js/login.js"></script>
{% endblock %}

{% block loginbody %}

    <div class="logo_box">
        <h3 style="text-align: center">欢迎你</h3>
        <form action="{{ url_for('login') }}" method="post">
            <div class="input_outer">
                <span class="u_user"></span>
                <input id="uname" class="text" style="color: wheat" type="text" placeholder="请输入账号" name="username">
            </div>
            <div class="input_outer">
                <span class="us_uer"></span>
                <input id="upass" class="text" style="color:wheat ; position:absolute; z-index:100;"
                       value="" type="password" placeholder="请输入密码" name="password">
            </div>
            <div class="errorText" id="error_box" style="color: red"><br></div>
            <div>
                <button onclick="return fnLogin()" class="lb1" style="color:black">登录</button>
            </div>
        </form>
    </div>
{% endblock %}

import os
DEBUG = True

SECRET_KEY = os.urandom(24)

DIALECT = 'mysql'
DRIVER = 'mysqldb'
USERNAME = 'root'
PASSWORD = 'ROOT'
HOST = '127.0.0.1'
DATABASE = 'mytest'


SQLALCHEMY_DATABASE_URI = 'mysql+pymysql://root:@127.0.0.1:3306/mytest?charset=utf8'
SQLALCHEMY_TRACK_MODIFICATIONS = False