python之crawlspider初探

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

# -*- 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("<!--TitleStart-->(.*?)<!--TitleEnd-->",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

巴特西

python之crawlspider初探

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