场景2的实现：

数据指纹

使用详情页的url充当数据指纹即可。

创建爬虫爬虫文件：

cd project_name（进入项目目录）
scrapy genspider 爬虫文件的名称（自定义一个名字即可）起始url
- （例如：scrapy genspider first www.xxx.com）
创建成功后，会在爬虫文件夹下生成一个py的爬虫文件

进入爬虫文件：

cd 爬虫文件的名称（即自定义的名字）

爬虫文件

import scrapy

import redis

import random

from ..items import Zlsdemo2ProItem

class JianliSpider(scrapy.Spider):

    name = "jianli"

    # allowed_domains = ["www.xxx.com"]

    start_urls = ["https://sc.chinaz.com/jianli/free.html"]

        # 连接数据库

    conn = redis.Redis(

        host='127.0.0.1',

        port=6379,

    )

    def parse(self, response):

        div_list = response.xpath('//*[@id="container"]/div')

        for div in div_list:

            title = div.xpath('./p/a/text()').extract_first()

            detail_url = div.xpath('./p/a/@href').extract_first()

            # print(title, detail_url)

            ex = self.conn.sadd('data_id', detail_url)

            #建立item对象

            item = Zlsdemo2ProItem()

            item['title'] = title#将title传给item

            if ex == 1:#数据库中没有存储爬取到的数据

                print('有最新数据更新，正在采集中......')

                #做请求传参，将title通过meta传递给parse_detail函数

                yield scrapy.Request(url=detail_url,callback=self.parse_detail,meta={'item':item})

            else:#数据库中已存储爬取到的数据

                print('暂无数据更新！')

    def parse_detail(self,response):

        item = response.meta['item']

        download_li = response.xpath('//*[@id="down"]/div[2]/ul/li')

        download_urls = []

        for li in download_li:

            download_url_e = li.xpath('./a/@href').extract_first()

            download_urls.append(download_url_e)

        download_url = random.choice(download_urls)

        item['download_url'] = download_url

        yield item

items.py

# Define here the models for your scraped items

#

# See documentation in:

# https://docs.scrapy.org/en/latest/topics/items.html

import scrapy

class Zlsdemo2ProItem(scrapy.Item):

    # define the fields for your item here like:

    # name = scrapy.Field()

    title = scrapy.Field()

    download_url = scrapy.Field()

pipelines.py

# Define your item pipelines here

#

# Don't forget to add your pipeline to the ITEM_PIPELINES setting

# See: https://docs.scrapy.org/en/latest/topics/item-pipeline.html

# useful for handling different item types with a single interface

from itemadapter import ItemAdapter

class Zlsdemo2ProPipeline:

    def process_item(self, item, spider):

        conn = spider.conn

        conn.lpush('data1', item)

        return item

settings

# Scrapy settings for zlsDemo2Pro project

#

# For simplicity, this file contains only settings considered important or

# commonly used. You can find more settings consulting the documentation:

#

#     https://docs.scrapy.org/en/latest/topics/settings.html

#     https://docs.scrapy.org/en/latest/topics/downloader-middleware.html

#     https://docs.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = "zlsDemo2Pro"

SPIDER_MODULES = ["zlsDemo2Pro.spiders"]

NEWSPIDER_MODULE = "zlsDemo2Pro.spiders"

# Crawl responsibly by identifying yourself (and your website) on the user-agent

USER_AGENT : "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.163 Safari/537.36"

# Obey robots.txt rules

ROBOTSTXT_OBEY = False

LOG_LEVEL = 'ERROR'

LOG_LEVEL = 'WARNING'

# Configure maximum concurrent requests performed by Scrapy (default: 16)

#CONCURRENT_REQUESTS = 32

# Configure a delay for requests for the same website (default: 0)

# See https://docs.scrapy.org/en/latest/topics/settings.html#download-delay

# See also autothrottle settings and docs

#DOWNLOAD_DELAY = 3

# The download delay setting will honor only one of:

#CONCURRENT_REQUESTS_PER_DOMAIN = 16

#CONCURRENT_REQUESTS_PER_IP = 16

# Disable cookies (enabled by default)

#COOKIES_ENABLED = False

# Disable Telnet Console (enabled by default)

#TELNETCONSOLE_ENABLED = False

# Override the default request headers:

#DEFAULT_REQUEST_HEADERS = {

#    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",

#    "Accept-Language": "en",

#}

# Enable or disable spider middlewares

# See https://docs.scrapy.org/en/latest/topics/spider-middleware.html

#SPIDER_MIDDLEWARES = {

#    "zlsDemo2Pro.middlewares.Zlsdemo2ProSpiderMiddleware": 543,

#}

# Enable or disable downloader middlewares

# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html

#DOWNLOADER_MIDDLEWARES = {

#    "zlsDemo2Pro.middlewares.Zlsdemo2ProDownloaderMiddleware": 543,

#}

# Enable or disable extensions

# See https://docs.scrapy.org/en/latest/topics/extensions.html

#EXTENSIONS = {

#    "scrapy.extensions.telnet.TelnetConsole": None,

#}

# Configure item pipelines

# See https://docs.scrapy.org/en/latest/topics/item-pipeline.html

ITEM_PIPELINES = {

   "zlsDemo2Pro.pipelines.Zlsdemo2ProPipeline": 300,

}

# Enable and configure the AutoThrottle extension (disabled by default)

# See https://docs.scrapy.org/en/latest/topics/autothrottle.html

#AUTOTHROTTLE_ENABLED = True

# The initial download delay

#AUTOTHROTTLE_START_DELAY = 5

# The maximum download delay to be set in case of high latencies

#AUTOTHROTTLE_MAX_DELAY = 60

# The average number of requests Scrapy should be sending in parallel to

# each remote server

#AUTOTHROTTLE_TARGET_CONCURRENCY = 1.0

# Enable showing throttling stats for every response received:

#AUTOTHROTTLE_DEBUG = False

# Enable and configure HTTP caching (disabled by default)

# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html#httpcache-middleware-settings

#HTTPCACHE_ENABLED = True

#HTTPCACHE_EXPIRATION_SECS = 0

#HTTPCACHE_DIR = "httpcache"

#HTTPCACHE_IGNORE_HTTP_CODES = []

#HTTPCACHE_STORAGE = "scrapy.extensions.httpcache.FilesystemCacheStorage"

# Set settings whose default value is deprecated to a future-proof value

REQUEST_FINGERPRINTER_IMPLEMENTATION = "2.7"

TWISTED_REACTOR = "twisted.internet.asyncioreactor.AsyncioSelectorReactor"

FEED_EXPORT_ENCODING = "utf-8"

巴特西

Day 22 22.1.2：增量式爬虫 - 场景2的实现

场景2的实现：

数据指纹

创建爬虫爬虫文件：

进入爬虫文件：

爬虫文件

items.py

pipelines.py

settings

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