python之crawlspider初探

谁践踏了优雅 2021-12-10 13:59 251阅读 0赞

**注意点：**

"""
            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
        """

1、创建工程

scrapy startproject zjh

2、创建项目

scrapy genspider -t crawl circ bxjg.circ.gov.cn
    与scrapy不同的是添加了-t crawl参数

3、settings文件添加日志级别，USER\_AGENT

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

# -*- 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'

4、circ.py文件提取数据

# -*- 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

5、扩展知识

![1170199-20190626100625366-28417719.png][]

转载于:https://www.cnblogs.com/ywjfx/p/11088293.html

[ContractedBlock.gif]: https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20211210/82c2bf1be0eb43b0bbd577f859f4a377.png
[1170199-20190626100625366-28417719.png]: /images/20211210/1b39e9f6a22c423bbd1011352a5a3967.png