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