python之crawlspider初探

注意点：

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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">""" 1、用命令创建一个crawlspider的模板：scrapy genspider -t crawl <爬虫名> <all_domain>,也可以手动创建 2、CrawlSpider中不能再有以parse为名字的数据提取方法，这个方法被CrawlSpider用来实现基础url提取等功能 3、一个Rule对象接受很多参数，首先第一个是包含url规则的LinkExtractor对象， 常有的还有callback(制定满足规则的解析函数的字符串)和follow(response中提取的链接是否需要跟进) 4、不指定callback函数的请求下，如果follow为True,满足rule的url还会继续被请求 5、如果多个Rule都满足某一个url,会从rules中选择第一个满足的进行操作 """</pre>

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1、创建工程

<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">scrapy startproject zjh</pre>

2、创建项目

<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;">scrapy genspider -t crawl circ bxjg.circ.gov.cn 与scrapy不同的是添加了-t crawl参数</pre>

3、settings文件添加日志级别，USER_AGENT

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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;"># -- coding: utf-8 --

Scrapy settings for zjh project

For simplicity, this file contains only settings considered important or # commonly used. You can find more settings consulting the documentation:

https://doc.scrapy.org/en/latest/topics/settings.html # https://doc.scrapy.org/en/latest/topics/downloader-middleware.html # https://doc.scrapy.org/en/latest/topics/spider-middleware.html

BOT_NAME = 'zjh' SPIDER_MODULES = ['zjh.spiders'] NEWSPIDER_MODULE = 'zjh.spiders' LOG_LEVEL = "WARNING"

Crawl responsibly by identifying yourself (and your website) on the user-agent #USER_AGENT = 'zjh (+http://www.yourdomain.com)'

USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36'

Obey robots.txt rules

ROBOTSTXT_OBEY = True # 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://doc.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://doc.scrapy.org/en/latest/topics/spider-middleware.html #SPIDER_MIDDLEWARES = { # 'zjh.middlewares.ZjhSpiderMiddleware': 543, #}

Enable or disable downloader middlewares # See https://doc.scrapy.org/en/latest/topics/downloader-middleware.html #DOWNLOADER_MIDDLEWARES = { # 'zjh.middlewares.ZjhDownloaderMiddleware': 543, #}

Enable or disable extensions # See https://doc.scrapy.org/en/latest/topics/extensions.html #EXTENSIONS = { # 'scrapy.extensions.telnet.TelnetConsole': None, #}

Configure item pipelines # See https://doc.scrapy.org/en/latest/topics/item-pipeline.html #ITEM_PIPELINES = { # 'zjh.pipelines.ZjhPipeline': 300, #}

Enable and configure the AutoThrottle extension (disabled by default) # See https://doc.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://doc.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'</pre>

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4、circ.py文件提取数据

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<pre style="margin: 0px; padding: 0px; white-space: pre-wrap; overflow-wrap: break-word; font-family: "Courier New" !important; font-size: 12px !important;"># -- coding: utf-8 -- import scrapy from scrapy.linkextractors import LinkExtractor from scrapy.spiders import CrawlSpider, Rule import re class CircSpider(CrawlSpider): name = 'circ' allowed_domains = ['bxjg.circ.gov.cn'] start_urls = ['http://bxjg.circ.gov.cn/web/site0/tab5240/module14430/page1.htm'] #定义提取url地址规则 rules = ( #一个Rule一条规则，LinkExtractor表示链接提取器，提取url地址 #allow，提取的url,url不完整，但是crawlspider会帮我们补全，然后再请求 #callback 提取出来的url地址的response会交给callback处理 #follow 当前url地址的响应是否重新将过rules来提取url地址 Rule(LinkExtractor(allow=r'/web/site0/tab5240/info\d+.htm'), callback='parse_item'), #详情页数据,不需要follow Rule(LinkExtractor(allow=r'/web/site0/tab5240/module14430/page\d+.htm'),follow=True), # 下一页,不需要callback处理，但是需要follow不断循环翻页 ) #parse函数有特殊功能，不能定义 def parse_item(self, response): item = {} item["title"]= re.findall("(.*?)",response.body.decode())[0] item["publish_date"] =re.findall("发布时间：20\d{2}-\d{2}-\d{2}",response.body.decode())[0] print(item) #也可以使用Request()自动构造请求 # yield scrapy.Request( # url, # callback=parse_detail # meta={"item":item} # ) def parse_detail(self,response): pass</pre>

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5、扩展知识