python 爬虫 实现增量去重和定时爬取实例

前言： 在爬虫过程中，我们可能需要重复的爬取同一个网站，为了避免重复的数据存入我们的数据库中 通过实现增量去重 去解决这一问题 本文还针对了那些需要实时更新的网站 增加了一个定时爬取的功能；

本文作者同开源中国（殊途同归_）；

解决思路：

1.获取目标url

2.解析网页

3.存入数据库（增量去重）

4.异常处理

5.实时更新（定时爬取）

下面为数据库的配置 mysql_congif.py：

import pymysql

def insert_db(db_table, issue, time_str, num_code):
 host = '127.0.0.1'
 user = 'root'
 password = 'root'
 port = 3306
 db = 'lottery'
 data_base = pymysql.connect(host=host, user=user, password=password, port=port, db=db)
 cursor = data_base.cursor()
 try:
   sql = "INSERT INTO ％s VALUES ('％s','％s','％s')" ％ (db_table, issue, time_str, num_code)
   cursor.execute(sql)
   data_base.commit()
 except ValueError as e:
   print(e)
   data_base.rollback()
 finally:
   cursor.close()
   data_base.close()

def select_db(issue, db_table):
 host = '127.0.0.1'
 user = 'root'
 password = 'root'
 port = 3306
 db = 'lottery'
 data_base = pymysql.connect(host=host, user=user, password=password, port=port, db=db)
 cursor = data_base.cursor()
 try:
   sql = "SELECT '％s' FROM ％s " ％ (issue, db_table)
   cursor.execute(sql)
   data_base.commit()
 except ValueError as e:
   print(e)
   data_base.rollback()
 finally:
   return issue

接下来是主要代码 test.py：

# 使用bs4进行网页解析
# 实现了增量去重
# 实现了定时爬取
import datetime
import time

from bs4 import BeautifulSoup
import requests

from mysql_config import insert_db
from mysql_config import select_db

def my_test():
 db_table = 'lottery_table'
 url = 'http://kj.13322.com/kl10_dkl10_history_dtoday.html'
 res = requests.get(url)
 content = res.content
 soup = BeautifulSoup(content, 'html.parser', from_encoding='utf8')
 c_t = soup.select('#trend_table')[0]
 trs = c_t.contents[4:]
 for tr in trs:
   if tr == '\n':
     continue
   tds = tr.select('td')
   issue = tds[1].text
   time_str = tds[0].text
   num_code = tr.table.text.replace('\n0', ',').replace('\n', ',').strip(',')
   print('期号：％s\t时间：％s\t号码:％s' ％ (str(issue), str(time_str), str(num_code)))
   issue_db = select_db(issue, db_table)
   try:
     if issue_db == issue:
       insert_db(db_table, issue_db, time_str, num_code)
       print('添加％s到％s成功' ％ (issue_db, db_table))
   except Exception as e:
     print('％s 已经存在！' ％ issue_db)
     print(e)

if __name__ == '__main__':
 flag = 0
 now = datetime.datetime.now()
 sched_time = datetime.datetime(now.year, now.month, now.day, now.hour, now.minute, now.second) +\
        datetime.timedelta(seconds=3)
 while True:
   now = datetime.datetime.now()
   if sched_time < now:
     time.sleep(3)
     print(now)
     my_test()
     flag = 1
   else:
     if flag == 1:
       sched_time = sched_time + datetime.timedelta(minutes=2)
       flag = 0

来源：https://blog.csdn.net/X_Special/article/details/80989345