Python轮询机制控制LED与Web投票系统实现

陆遥

发布时间：2026-10-12 | 4人浏览过

原创

本文通过Python实例详解轮询与长轮询机制。首先展示利用串口通信读取Arduino数据并控制LED亮灭的代码逻辑，随后对比传统轮询与长轮询在Web投票系统中的实现差异。通过Flask后端与前端JavaScript交互，解析两种模式下的数据获取方式及性能特点，为开发者提供实用的技术参考。

以下直接展示核心代码实现，省略冗余说明。

# -*- coding:utf-8 -*- 
# File: ceshitianqi
 
import urllib2
import json
import time
import datetime
import serial 
import random
import os
import sys
 
APIKEY = 'ZPdLyl***=' #改成你的APIKEY
ser=serial.Serial("/dev/ttyUSB2",9600,timeout=1)
 
def read(key):
  ser.write(key)
  print("output:"+key)
  time.sleep(1)
  response = ser.readall()
  print(response)
  print(type(response))
  return response
 
def http_put(key):
  val = read(key) #获取Arduino的数据
  CurTime = datetime.datetime.now()
  url='http://api.heclouds.com/devices/**1/datapoints'
  #values={'datastreams':[{"id":"temp","datapoints":[{"at":CurTime.isoformat(),"value":val}]}]}
  print(type(val))
  if key== "a" :
   values={'datastreams':[{"id":"humidity","datapoints":[{"at":CurTime.isoformat(),"value":val}]}]}
  if key== "b" :
   values={'datastreams':[{"id":"temperature","datapoints":[{"at":CurTime.isoformat(),"value":val}]}]}
  jdata = json.dumps(values)         # 对数据进行JSON格式化编码
  #打印json内容
  print jdata
  request = urllib2.Request(url, jdata)
  request.add_header('api-key', APIKEY)
  request.get_method = lambda:'POST'     # 设置HTTP的访问方式
  request = urllib2.urlopen(request)
  return request.read()  
 
str = ("a","b")
while True:
	for i in str: 
		f = open('1.txt')
		e = f.read()
		if e == "1\n":
			ser.write("c")
		if e == "0\n":
			ser.write("d")
 
		f.close()  
		resp = http_put(i)
   		time.sleep(2)

轮询文件：1.txt

当文件内容为1时，LED点亮。

当文件内容为0时，LED关闭。

补充知识：Python笔记(轮询、长轮询)

一、轮询机制

后端视图文件：views.py

from flask import Flask,render_template,request,jsonify

app = Flask(__name__)

USERS = {
  '1':{'name':'贝贝','count':1},
  '2':{'name':'小东北','count':0},
  '3':{'name':'何伟明','count':0},
}

@app.route('/user/list')
def user_list():
  import time
  return render_template('user_list.html',users=USERS)

@app.route('/vote',methods=['POST'])
def vote():
  uid = request.form.get('uid')
  USERS[uid]['count'] += 1
  return "投票成功"

@app.route('/get/vote',methods=['GET'])
def get_vote():

  return jsonify(USERS)


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

前端HTML模板

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <style>
    li{
      cursor: pointer;
    }
  </style>
</head>
<body>
  <ul id="userList">
    {% for key,val in users.items() %}
      <li uid="{{key}}">{{val.name}} ({{val.count}})</li>
    {% endfor %}
  </ul>

  <script src="https://cdn.bootcss.com/jquery/3.3.0/jquery.min.js"></script>
  <script>

    $(function () {
      $('#userList').on('dblclick','li',function () {
        var uid = $(this).attr('uid');
        $.ajax({
          url:'/vote',
          type:'POST',
          data:{uid:uid},
          success:function (arg) {
            console.log(arg);
          }
        })
      });

    });


    /*
    获取投票信息
     */
    function get_vote() {
      $.ajax({
        url:'/get/vote',
        type:"GET",
        dataType:'JSON',
        success:function (arg) {
          $('#userList').empty();
          $.each(arg,function (k,v) {
            var li = document.createElement('li');
            li.setAttribute('uid',k);
            li.innerText = v.name + "(" + v.count + ')' ;
            $('#userList').append(li);
          })

        }
      })
    }


    setInterval(get_vote,3000);

  </script>
</body>
</html>

二、长轮询机制

后端视图文件：views.py

from flask import Flask,render_template,request,jsonify,session
import uuid
import queue

app = Flask(__name__)
app.secret_key = 'asdfasdfasd'


USERS = {
  '1':{'name':'贝贝','count':1},
  '2':{'name':'小东北','count':0},
  '3':{'name':'何伟明','count':0},
}

QUEQUE_DICT = {
}

@app.route('/user/list')
def user_list():
  user_uuid = str(uuid.uuid4())
  QUEQUE_DICT[user_uuid] = queue.Queue()

  session['current_user_uuid'] = user_uuid
  return render_template('user_list.html',users=USERS)

@app.route('/vote',methods=['POST'])
def vote():
  uid = request.form.get('uid')
  USERS[uid]['count'] += 1
  for q in QUEQUE_DICT.values():
    q.put(USERS)
  return "投票成功"


@app.route('/get/vote',methods=['GET'])
def get_vote():
  user_uuid = session['current_user_uuid']
  q = QUEQUE_DICT[user_uuid]

  ret = {'status':True,'data':None}
  try:
    users = q.get(timeout=5)
    ret['data'] = users
  except queue.Empty:
    ret['status'] = False

  return jsonify(ret)



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

前端HTML模板

<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <style>
    li{
      cursor: pointer;
    }
  </style>
</head>
<body>
  <ul id="userList">
    {% for key,val in users.items() %}
      <li uid="{{key}}">{{val.name}} ({{val.count}})</li>
    {% endfor %}
  </ul>

  <script src="https://cdn.bootcss.com/jquery/3.3.0/jquery.min.js"></script>
  <script>

    $(function () {
      $('#userList').on('click','li',function () {
        var uid = $(this).attr('uid');
        $.ajax({
          url:'/vote',
          type:'POST',
          data:{uid:uid},
          success:function (arg) {
            console.log(arg);
          }
        })
      });
      get_vote();
    });

    /*
    获取投票信息
     */
    function get_vote() {
      $.ajax({
        url:'/get/vote',
        type:"GET",
        dataType:'JSON',
        success:function (arg) {
          if(arg.status){
            $('#userList').empty();
              $.each(arg.data,function (k,v) {
                var li = document.createElement('li');
                li.setAttribute('uid',k);
                li.innerText = v.name + "(" + v.count + ')' ;
                $('#userList').append(li);
              })
          }
          get_vote();

        }
      })
    }

  </script>
</body>
</html>

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