增量式爬虫

概念：监测网站数据更新的情况，只会爬取网站最新更新出来的数据。

分析：

指定一个起始url

基于CrawlSpider获取其他页码链接

基于Rule将其他页码链接进行请求

从每一个页码对应的页面源码中解析出每一个电影详情页的URL

# -*- coding: utf-8 -*-
import scrapy
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule

from redis import Redis
from moviePro.items import MovieproItem
class MovieSpider(CrawlSpider):
    name = 'movie'
    # allowed_domains = ['www.ccc.com']
    start_urls = ['https://www.4567tv.tv/frim/index1.html']

    rules = (
        Rule(LinkExtractor(allow=r'/frim/index1-\d+\.html'), callback='parse_item', follow=True),
    )
    # 创建redis链接对象
    conn = Redis(host='127.0.0.1', port=6379)

    #用于解析每一个页码对应页面中的电影详情页的url
    def parse_item(self, response):
        li_list = response.xpath('/html/body/div[1]/div/div/div/div[2]/ul/li')
        for li in li_list:
            # 获取详情页的url
            detail_url = 'https://www.4567tv.tv' + li.xpath('./div/a/@href').extract_first()

            # 将详情页的url存入redis的set中
            ex = self.conn.sadd('urls', detail_url)
            if ex == 1:
                print('该url没有被爬取过，可以进行数据的爬取')
                yield scrapy.Request(url=detail_url, callback=self.parst_detail)
            else:
                print('数据还没有更新，暂无新数据可爬取！')

    # 解析详情页中的电影名称和类型，进行持久化存储
    def parst_detail(self, response):
        item = MovieproItem()
        item['name'] = response.xpath('/html/body/div[1]/div/div/div/div[2]/h1/text()').extract_first()
        item['desc'] = response.xpath('/html/body/div[1]/div/div/div/div[2]/p[5]/span[2]//text()').extract()
        item['desc'] = ''.join(item['desc'])
        yield item

核心：检测电影详情页的url之前有没有请求过

将爬取过的电影详情页的url存储

存储到redis的set数据结构

对详情页的url发起请求，然后解析出电影的名称和简介

进行持久化存储

# -*- coding: utf-8 -*-

# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: https://doc.scrapy.org/en/latest/topics/item-pipeline.html

from redis import Redis
class MovieproPipeline(object):
    conn = None
    def open_spider(self,spider):
        self.conn = spider.conn
    def process_item(self, item, spider):
        dic = {
            'name':item['name'],
            'desc':item['desc']
        }
        # print(dic)
        self.conn.lpush('movieData',dic)
        return item