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scrapy爬虫实例之爬取阳光政务网的问题反映模块

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需求

爬取阳光政务网的问题反映模块。主要练习翻页请求是怎么实现的。

怎么做

首先，观察element和html响应，发现element中有tbody标签，但是html响应里面没有tbody标签（这种情况比较多，所以看到tbody标签要额外小心）。写xpath一定要以html响应为准！
start_url要找对，今天我亲自体验了一把start_url都没有正确设置的情况下改xpath的痛苦之情😭
image.png
思路：

  1. 提取当前页面的数据和详情页的url
  2. scrapy.Request()发送详情页的请求，提取详情页数据
  3. 提取翻页的url，发送翻页请求，循环1-2步
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yield scrapy.Request(
                item["href"],
                callback=self.parse_detail,
                meta={"item": item}
            )

这部分代码是关键。功能是发送详情页请求，parse_detail是我们新定义的一个用于提取详情页数据的函数。meta用于传递当前的数据到parse_detail函数体，使用的场景是当前提取的是部分数据，需要将这部分的数据传递到callback函数体继续添加新的数据。
这个例子中，我们还用到了items模块，定义我们需要提取的数据字段。在爬虫代码中使用这个item时，需import。比如：
from sun.items import SunItem

代码

爬虫代码：wzsun.py

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# -*- coding: utf-8 -*-
import scrapy
from sun.items import SunItem

class WzsunSpider(scrapy.Spider):
    name = 'wzsun'
    allowed_domains = ['sun0769.com']
    start_urls = ['http://wz.sun0769.com/html/top/report.shtml']

    def parse(self, response):
        #1. 提取当前页面的数据和详情页的url
        tr_list = response.xpath("//div[@class='newsHead clearfix']/table[2]/tr")
        for tr in tr_list:
            item = SunItem()
            item["title"] = tr.xpath("./td[3]/a/@title").extract_first()
            # print(item["title"])
            item["href"] = tr.xpath("./td[3]/a/@href").extract_first()
            # print(item["href"])
            item["publish_date"] = tr.xpath("./td[last()]/text()").extract_first()
            # print(item["publish_date"])
        #2. scrapy.Request()发送详情页的请求，提取详情页数据
            yield scrapy.Request(
                item["href"],
                callback=self.parse_detail,
                meta={"item": item}
            )
        #3. 翻页
        next_url = response.xpath("//div[@class='pagination']//a[text()='>']/@href").extract_first()
        # print(next_url)
        if next_url is not None:
            yield scrapy.Request(
                next_url,
                callback=self.parse
            )

    def parse_detail(self,response):
        item = response.meta["item"]
        item["content"] = response.xpath("//div[@class='wzy1']/table[2]//td[@class='txt16_3']/text()").extract()
        # print(item["content"])
        item["content_img"] = response.xpath("//div[@class='wzy1']/table[2]//td[@class='txt16_3']//img/@src").extract()
        item["content_img"] = ["http://wz.sun0769.com"+i for i in item["content_img"]]
        # print(item["content_img"])
        # print(item)
        yield item

items.py：

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# -*- coding: utf-8 -*-

# Define here the models for your scraped items
#
# See documentation in:
# https://docs.scrapy.org/en/latest/topics/items.html

import scrapy


class SunItem(scrapy.Item):
    # define the fields for your item here like:
    title = scrapy.Field()
    publish_date = scrapy.Field()
    href = scrapy.Field()
    content = scrapy.Field()
    content_img = scrapy.Field()

pipelines.py：这里保存数据时，我们对提取的数据做了格式化，将content里面的\xa0和空格做了替换。此处复习了正则表达式的替换功能re.sub

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# -*- coding: utf-8 -*-

# 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
import re

class SunPipeline(object):
    def process_item(self, item, spider):
        item["content"] = self.process_content(item["content"]) #将content的数据做格式化
        print(item)
        return item

    def process_content(self, content):
        content = [re.sub(r"\xa0|\s","",i) for i in content] #去除\xa0和空格
        content = [i for i in content if len(i)>0] #去除列表中的空字符串
        return content

settings.py：

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# -*- coding: utf-8 -*-

# Scrapy settings for sun 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 = 'sun'

SPIDER_MODULES = ['sun.spiders']
NEWSPIDER_MODULE = 'sun.spiders'

LOG_LEVEL = 'WARNING'
# Crawl responsibly by identifying yourself (and your website) on the user-agent
USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.106 Safari/537.36'

# Obey robots.txt rules
ROBOTSTXT_OBEY = False

# 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 = {
#    'sun.middlewares.SunSpiderMiddleware': 543,
#}

# Enable or disable downloader middlewares
# See https://docs.scrapy.org/en/latest/topics/downloader-middleware.html
#DOWNLOADER_MIDDLEWARES = {
#    'sun.middlewares.SunDownloaderMiddleware': 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 = {
   'sun.pipelines.SunPipeline': 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'

在设置文件里，我们开启了USER_AGENT字段，设置了一个UA。

爬取的结果

image.png

总结

settings.py文件里面的ROBOTSTXT_OBEY = False意思是不遵循robots.txt的爬虫规则。
正则表达式中\s表示空格符号。
翻页请求是这样实现的：

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next_url = response.xpath("//div[@class='pagination']//a[text()='>']/@href").extract_first()
        # print(next_url)
        if next_url is not None:
            yield scrapy.Request(
                next_url,
                callback=self.parse
            )

xpath之后一定要记得使用.extract_first()或者.extract()。
a[text()='>'表示提取文本内容为>的a标签。

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