scrapy学习笔记(三):使用item与pipeline保存数据
scrapy下使用item才是正经方法。
在item中定义需要保存的内容,然后在pipeline处理item,爬虫流程就成了这样:
抓取 --> 按item规则收集需要数据 -->使用pipeline处理(存储等)
定义item,在items.py中定义抓取内容
# -*- coding: utf-8 -*-
# Define here the models for your scraped items
#
# See documentation in:
# http://doc.scrapy.org/en/latest/topics/items.html
import scrapy
class GetquotesItem(scrapy.Item):
# define the fields for your item here like:
# 定义我们需要抓取的内容:
# 1.名言内容
# 2.作者
# 3.标签
content = scrapy.Field()
author = scrapy.Field()
tags = scrapy.Field()
我们将数据库的配置信息保存在setting.py文件中,方便调用
MONGODB_HOST = 'localhost'
MONGODB_PORT = 27017
MONGODB_DBNAME = 'store_quotes2'
MONGODB_TABLE = 'quotes2'
另外,在setting.py文件中一点要将pipeline注释去掉,要不然pipeline不会起作用:
#ITEM_PIPELINES = {
# 'getquotes.pipelines.SomePipeline': 300,
#}
改成
ITEM_PIPELINES = {
'getquotes.pipelines.GetquotesPipeline': 300,
}
现在在pipeline.py中定义处理item方法:
# -*- coding: utf-8 -*-
# Define your item pipelines here
#
# Don't forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html
# 将setting导入,以使用定义内容
from scrapy.conf import settings
import pymongo
class GetquotesPipeline(object):
# 连接数据库
def __init__(self):
# 获取数据库连接信息
host = settings['MONGODB_HOST']
port = settings['MONGODB_PORT']
dbname = settings['MONGODB_DBNAME']
client = pymongo.MongoClient(host=host, port=port)
# 定义数据库
db = client[dbname]
self.table = db[settings['MONGODB_TABLE']]
# 处理item
def process_item(self, item, spider):
# 使用dict转换item,然后插入数据库
quote_info = dict(item)
self.table.insert(quote_info)
return item
相应的,myspider.py中的代码变化一下
import scrapy
import pymongo
# 别忘了导入定义的item
from getquotes.items import GetquotesItem
class myspider(scrapy.Spider):
# 设置爬虫名称
name = "get_quotes"
# 设置起始网址
start_urls = ['http://quotes.toscrape.com']
'''
# 配置client,默认地址localhost,端口27017
client = pymongo.MongoClient('localhost',27017)
# 创建一个数据库,名称store_quote
db_name = client['store_quotes']
# 创建一个表
quotes_list = db_name['quotes']
'''
def parse(self, response):
#使用 css 选择要素进行抓取,如果喜欢用BeautifulSoup之类的也可以
#先定位一整块的quote,在这个网页块下进行作者、名言,标签的抓取
for quote in response.css('.quote'):
'''
# 将页面抓取的数据存入mongodb,使用insert
yield self.quotes_list.insert({
'author' : quote.css('small.author::text').extract_first(),
'tags' : quote.css('div.tags a.tag::text').extract(),
'content' : quote.css('span.text::text').extract_first()
})
'''
item = GetquotesItem()
item['author'] = quote.css('small.author::text').extract_first()
item['content'] = quote.css('span.text::text').extract_first()
item['tags'] = quote.css('div.tags a.tag::text').extract()
yield item
# 使用xpath获取next按钮的href属性值
next_href = response.xpath('//li[@class="next"]/a/@href').extract_first()
# 判断next_page的值是否存在
if next_href is not None:
# 如果下一页属性值存在,则通过urljoin函数组合下一页的url:
# www.quotes.toscrape.com/page/2
next_page = response.urljoin(next_href)
#回调parse处理下一页的url
yield scrapy.Request(next_page,callback=self.parse)