【python爬虫学习 】python3.7 scrapy 安装，demo实例，实践：爬取百度

1. pip 安装 pip install scrapy
2. 可能的问题：
   问题/解决：error: Microsoft Visual C++ 14.0 is required.

3. 实例demo教程 中文教程文档
   第一步：创建项目目录

   scrapy startproject tutorial

   第二步：进入tutorial创建spider爬虫

   scrapy genspider baidu www.baidu.com

   第三步：创建存储容器，复制项目下的items.py重命名为BaiduItems

   # -*- coding: utf-8 -*-
   
   # Define here the models for your scraped items
   #
   # See documentation in:
   # https://doc.scrapy.org/en/latest/topics/items.html
   
   import scrapy
   
   class BaiduItems(scrapy.Item):
       # define the fields for your item here like:
       # name = scrapy.Field()
       title = scrapy.Field()
       link = scrapy.Field()
       desc = scrapy.Field()
       pass

   第四步：修改spiders/baidu.py xpath提取数据

   # -*- coding: utf-8 -*-
   import scrapy
   # 引入数据容器
   from tutorial.BaiduItems import BaiduItems
   
   class BaiduSpider(scrapy.Spider):
       name = 'baidu'
       allowed_domains = ['www.readingbar.net']
       start_urls = ['http://www.readingbar.net/']
       def parse(self, response):
           for sel in response.xpath('//ul/li'):
               item = BaiduItems()
               item['title'] = sel.xpath('a/text()').extract()
               item['link'] = sel.xpath('a/@href').extract()
               item['desc'] = sel.xpath('text()').extract()
               yield item
           pass

   第五步：解决百度首页网站抓取空白问题,设置setting.py

   # 设置用户代理
   USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36'
   
   # 解决 robots.txt 相关debug
   ROBOTSTXT_OBEY = False
   # scrapy 解决数据保存乱码问题
   FEED_EXPORT_ENCODING = 'utf-8'

   最后一步：开始爬取数据命令并保存数据为指定的文件
   执行的时候可能报错：No module named 'win32api' 可以下载指定版本安装

   scrapy crawl baidu -o baidu.json

4. 深度爬取百度首页及导航菜单相关页内容

   # -*- coding: utf-8 -*-
   import scrapy
   
   from scrapyProject.BaiduItems import BaiduItems
   
   class BaiduSpider(scrapy.Spider):
       name = 'baidu'
       # 由于tab包含其他域名,需要添加域名否则无法爬取
       allowed_domains = [
           'www.baidu.com',
           'v.baidu.com',
           'map.baidu.com',
           'news.baidu.com',
           'tieba.baidu.com',
           'xueshu.baidu.com'
       ]
       start_urls = ['https://www.baidu.com/']
       def parse(self, response):
           item = BaiduItems()
           item['title'] = response.xpath('//title/text()').extract()
           yield item
           for sel in response.xpath('//a[@class="mnav"]'):
               item = BaiduItems()
               item['nav'] = sel.xpath('text()').extract()
               item['href'] = sel.xpath('@href').extract()
               yield item
               # 根据提取的nav地址建立新的请求并执行回调函数
               yield scrapy.Request(item['href'][0],callback=self.parse_newpage)
           pass
       # 深度提取tab网页标题信息
       def parse_newpage(self, response):
           item = BaiduItems()
           item['title'] = response.xpath('//title/text()').extract()
           yield item
           pass

5. 绕过登录进行爬取
   a.解决图片验证 pytesseract