Scrapy代码实战

1.Spider爬虫代码

 1 # -*- coding: utf-8 -*-
 2 import scrapy
 3 from yszd.items import YszdItem
 4 
 5 
 6 class YszdSpiderSpider(scrapy.Spider):
 7     # 爬虫名称，启动爬虫时必须的参数
 8     name = 'yszd_spider'
 9     # 爬取域范围，运行爬虫在这个域名下爬取数据（可选）
10     allowed_domains = ['itcast.cn']
11     # 起始url列表，爬虫执行后第一批请求将从这个列表里获取
12     start_urls = ['http://www.itcast.cn/channel/teacher.shtml']
13 
14     def parse(self, response):
15         # //表示跳级定位，即对当前元素的所有子节点进行查找，一般开头都是使用跳级定位
16         # div[@class='li_txt'] : 查找div且属性class='li_txt'的
17         node_list = response.xpath("//div[@class='li_txt']")
18         # 存储所有item字段
19         # items = []
20         for node in node_list:
21             # 创建item字段对象用来存储信息
22             item = YszdItem()
23             # extract() : 将xpath对象转换为Unicode字符串
24             name = node.xpath("./h3/text()").extract()
25             title = node.xpath("./h4/text()").extract()
26             info = node.xpath("./p/text()").extract()
27             
28             item['name'] = name[0]
29             item['title'] = title[0]
30             item['info'] = info[0]
31 
32             yield item
33             # items.append(item)

2.Item代码（定义爬取的字段）

 1 # -*- coding: utf-8 -*-
 2 
 3 # Define here the models for your scraped items
 4 #
 5 # See documentation in:
 6 # https://doc.scrapy.org/en/latest/topics/items.html
 7 
 8 import scrapy
 9 
10 
11 class YszdItem(scrapy.Item):
12     name = scrapy.Field()
13     title = scrapy.Field()
14     info = scrapy.Field()

3.Pipelines管道代码

 1 # -*- coding: utf-8 -*-
 2 
 3 # Define your item pipelines here
 4 #
 5 # Don't forget to add your pipeline to the ITEM_PIPELINES setting
 6 # See: https://doc.scrapy.org/en/latest/topics/item-pipeline.html
 7 
 8 import json
 9 
10 
11 class YszdPipeline(object):
12     def __init__(self):
13         self.f = open("yszd.json", "w")
14 
15     def process_item(self, item, spider):
16         # ensure_ascii默认是True，会把内容转换为unicode
17         text = json.dumps(dict(item), ensure_ascii=False) + "
"
18         self.f.write(text)
19         return item
20 
21     def close_spider(self, spider):
22         self.f.close()

4.setting代码（开启管道，300表示优先级，越小优先级越高）

5.运行爬虫

　　执行命令：scrapy crawl yszd_spider

　　注意：yszd_spider为你定义爬虫的名称，与1中的第8行代码对应！

6.执行结果