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
 

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