1. 新建一个socket TCP服务端，为了实现浏览器连接服务端，
       让服务端消息符合HTTP协议（在开头加一个conn.send(b'HTTP/1.1 200 OK \r\n\r\n')）
    2. 想要实现网页地址加不同的后缀能显示不同的内容（如：127.0.0.1:8080/index，网页显示index）
    3. data = conn.recv(1024), 打印该data，发现里面装的二进制存的是数据格式之请求
    4. 将data解码为字符串，字符串二次切分（1：'\r\n', 2:' '）列表list索引1取到的就是地址后缀
    5. if list[1] == '/index': conn.send('index');这样就实现了
    6. 还不够方便，要实现并发就要导入模块，这使用wsgire模块(自动将请求与接收的数据封装成符合HTTP协议的格式)
      （使用同socketserver有点像，第二个参数传run(socketserver是传一个类名，这里run是函数名)）
    7. run会接收到两个参数env, response，env就是之前data解码后的字符串，不过被自动切分并组成大字典的形式，
       env['PATH_INFO']就是后缀名，response用来设置HTTP响应的状态码和头信息
    8. 后缀名多了之后要写一堆elif判断，所以抽离出一个对应关系urls = [('后缀名', 函数名), ('后缀名', 函数名)]
    9. urls叫路由，函数叫做视图函数，我们将它们各放入其他模块里（urls.py, views.py），之后导入模块即可。
    10. 为了后端数据（比如字典）发给前端使用，引入jinja2模块。
        from jinja2 import Template
        def reg(env):
            user_dic = {'name': 'jason', 'password': 123}
            with open('html文件名', 'r', encoding='utf-8') as f:
                data = f.read()
            tem = Template(data)  //提交渲染页面
            return tem.render(user_dic=user_dic)

import socket


server = socket.socket()
server.bind(('127.0.0.1', 8081))
server.listen(5)

while True:
    conn, addr = server.accept()
    # 一定要先接收一下信息，因为网页作为客户端连接会发送GET请求
    data = conn.recv(1024)
    # 先发送一个头信息，让接下去发送的消息符合HTTP协议
    conn.send(b'HTTP/1.1 200 OK \r\n\r\n')
    conn.send(b'hello')
    conn.close()

import socket


server = socket.socket()
server.bind(('127.0.0.1', 8081))
server.listen(5)

while True:
    conn, addr = server.accept()
    # 一定要先接收一下信息，因为网页作为客户端连接会发送GET请求
    data = conn.recv(1024)
    # 将data输出，然后复制出来看看，可以找到规律用split切分
    print(data)
    data = data.decode('utf-8').split('\r\n')[0]
    current_path = data.split(' ')[1]
    # 先发送一个头信息，让接下去发送的消息符合HTTP协议
    conn.send(b'HTTP/1.1 200 OK \r\n\r\n')
    if current_path == '/index':
        conn.send(b'index')
    else:
        conn.send(b'hello')
    conn.close()

from wsgiref.simple_server import make_server


def run(env, response):
    # response是response用来设置HTTP响应的状态码和头信息，状态码固定'200 OK'
    # 状态码类似我们之前的conn.send(b'HTTP/1.1 200 OK \r\n\r\n')
    # 然后头信息固定是列表里面套元组的形式，元组里必须要有两个元素，元组的个数至少一个
    response('200 ok', [('name', 'egon'), ('password', '123')])
    current_path = env['PATH_INFO']
    if current_path == '/index':
        res = 'index'
    else:
        res = '404 not find'
    # return的也要求是列表里面一个二进制数据
    return [res.encode('utf-8')]


if __name__ == '__main__':
    server = make_server('127.0.0.1', 8081, run)
    server.serve_forever()

from wsgiref.simple_server import make_server


def index():
    return 'index'


urls = [
    ('/index', index)
]


def error():
    return '404 not found'


def run(env, response):
    # response响应状态码和头信息
    response('200 ok', [('name', 'egon'), ('password', '123')])
    # 取出地址后缀
    current_path = env['PATH_INFO']
    func = None
    for url in urls:
        if current_path == url[0]:
            func = url[1]
            # 只要找到了就终止for循环
            break
    if func:
        res = func()
    else:
        res = error()
    return [res.encode('utf-8')]


if __name__ == '__main__':
    server = make_server('127.0.0.1', 8080, run)
    server.serve_forever()

from wsgiref.simple_server import make_server
from urls import *


def run(env, response):
    response('200 ok', [('name', 'egon'), ('password', '123')])
    current_path = env['PATH_INFO']
    func = None
    for url in urls:
        if current_path == url[0]:
            func = url[1]
            break
    if func:
        res = func()
    else:
        res = error()
    return [res.encode('utf-8')]


if __name__ == '__main__':
    server = make_server('127.0.0.1', 8080, run)
    server.serve_forever()

import time
from jinja2 import Template
import pymysql


def index():
    return 'index'


def error():
    return '404 not found'


def get_time():
    with open('templates/get_time.html', 'r', encoding='utf-8') as f:
        data = f.read()
    res = data.replace('time', time.strftime('%Y-%m-%d %X'))
    return res


def get_user():
    user_dic = {'name': 'egon', 'password': '123'}
    with open('templates/get_user.html', 'r', encoding='utf-8') as f:
        data = f.read()
    tem = Template(data)
    return tem.render(user_dic=user_dic)


def get_db():
    # 连接数据库
    conn = pymysql.connect(
        host='127.0.0.1',
        port=3306,
        user='root',
        password='root',
        database='day54',
        charset='utf8',
        autocommit=True
    )
    cursor = conn.cursor(pymysql.cursors.DictCursor)
    sql = 'select * from web_frame'
    cursor.execute(sql)
    # 得到数据库里web_frame表所有的数据：[{}, {}, {}]
    user_list = cursor.fetchall()
    with open('templates/get_db.html', 'r', encoding='utf-8') as f:
        data = f.read()
    tem = Template(data)
    return tem.render(user_list=user_list)

from views import *

urls = [
    ('/index', index),
    ('/get_time', get_time),
    ('/get_user', get_user),
    ('/get_db', get_db)
]

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>get_time</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/js/bootstrap.min.js"></script>
    <link href="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
@@time@@
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>get_user</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/js/bootstrap.min.js"></script>
    <link href="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet">
</head>
<body>
<p>{{user_dic}}</p>
<p>{{user_dic.name}}</p>
<p>{{user_dic['name']}}</p>
<p>{{user_dic.get('password')}}</p>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>get_db</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.min.js"></script>
    <script src="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/js/bootstrap.min.js"></script>
    <link href="https://cdn.bootcss.com/twitter-bootstrap/3.4.1/css/bootstrap.min.css" rel="stylesheet">
    <style>
        th {
            text-align: center;
        }
    </style>
</head>
<body>
<div class="container">
    <div class="row">
        <div class="col-md-8">
            <table class="table table-bordered table-striped table-hover">
                <thead>
                    <tr>
                        <th>id</th>
                        <th>框架名称</th>
                        <th>socket</th>
                        <th>路由器与视图函数</th>
                        <th>模块渲染</th>
                    </tr>
                </thead>
                <tbody class="text-center">
                    {%for user_dic in user_list%}
                        <tr>
                            <td>{{user_dic['id']}}</td>
                            <td>{{user_dic['框架名称']}}</td>
                            <td>{{user_dic['socket']}}</td>
                            <td>{{user_dic['路由器与视图函数']}}</td>
                            <td>{{user_dic['模块渲染']}}</td>
                        </tr>
                    {%endfor%}
                </tbody>
            </table>
        </div>
    </div>
</div>
</body>
</html>