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scrapy爬虫成长日记之创建工程-抽取数据-保存为json格式的数据

  在安装完scrapy以后,相信大家都会跃跃欲试想定制一个自己的爬虫吧?我也不例外,下面详细记录一下定制一个scrapy工程都需要哪些步骤。如果你还没有安装好scrapy,又或者为scrapy的安装感到头疼和不知所措,可以参考下前面的文章安装python爬虫scrapy踩过的那些坑和编程外的思考。这里就拿博客园来做例子吧,抓取博客园的博客列表并保存到json文件。

环境:CentOS 6.0 虚拟机

  scrapy(如未安装可参考安装python爬虫scrapy踩过的那些坑和编程外的思考

1、创建工程cnblogs

[root@bogon share]# scrapy startproject cnblogs
2015-06-10 15:45:03 [scrapy] INFO: Scrapy 1.0.0rc2 started (bot: scrapybot)
2015-06-10 15:45:03 [scrapy] INFO: Optional features available: ssl, http11
2015-06-10 15:45:03 [scrapy] INFO: Overridden settings: {}
New Scrapy project 'cnblogs' created in:
    /mnt/hgfs/share/cnblogs

You can start your first spider with:
    cd cnblogs
    scrapy genspider example example.com

2、查看下工程的结构

[root@bogon share]# tree cnblogs/
cnblogs/
├── cnblogs
│   ├── __init__.py
│   ├── items.py #用于定义抽取网页结构
│   ├── pipelines.py #将抽取的数据进行处理
│   ├── settings.py #爬虫配置文件
│   └── spiders
│       └── __init__.py
└── scrapy.cfg #项目配置文件

3、定义抽取cnblogs的网页结构,修改items.py

这里我们抽取四个内容:

  • 文章标题
  • 文章链接
  • 文在所在的列表页URL
  • 摘要
[root@bogon cnblogs]# vi cnblogs/items.py
# -*- 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 CnblogsItem(scrapy.Item):
    # define the fields for your item here like:
    # name = scrapy.Field()
    title = scrapy.Field()
    link = scrapy.Field()
    desc = scrapy.Field()
    listUrl = scrapy.Field()
    pass

4、创建spider

[root@bogon cnblogs]# vi cnblogs/spiders/cnblogs_spider.py

#coding=utf-8
import re
import json
from scrapy.selector import Selector
try:
    from scrapy.spider import Spider
except:
    from scrapy.spider import BaseSpider as Spider
from scrapy.utils.response import get_base_url
from scrapy.utils.url import urljoin_rfc
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor as sle
from cnblogs.items import *

class CnblogsSpider(CrawlSpider):
    #定义爬虫的名称
    name = "CnblogsSpider"
    #定义允许抓取的域名,如果不是在此列表的域名则放弃抓取
    allowed_domains = ["cnblogs.com"]
    #定义抓取的入口url
    start_urls = [
        "http://www.cnblogs.com/rwxwsblog/default.html?page=1"
    ]
    # 定义爬取URL的规则,并指定回调函数为parse_item
    rules = [
        Rule(sle(allow=("/rwxwsblog/default.html\?page=\d{1,}")), #此处要注意?号的转换,复制过来需要对?号进行转义。
                         follow=True,
                         callback='parse_item')
    ]
    #print "**********CnblogsSpider**********"
    #定义回调函数
    #提取数据到Items里面,主要用到XPath和CSS选择器提取网页数据
    def parse_item(self, response):
        #print "-----------------"
        items = []
        sel = Selector(response)
        base_url = get_base_url(response)
        postTitle = sel.css('div.day div.postTitle')
        #print "=============length======="
        postCon = sel.css('div.postCon div.c_b_p_desc')
        #标题、url和描述的结构是一个松散的结构,后期可以改进
        for index in range(len(postTitle)):
            item = CnblogsItem()
            item['title'] = postTitle[index].css("a").xpath('text()').extract()[0]
            #print item['title'] + "***************\r\n"
            item['link'] = postTitle[index].css('a').xpath('@href').extract()[0]
            item['listUrl'] = base_url
            item['desc'] = postCon[index].xpath('text()').extract()[0]
            #print base_url + "********\n"
            items.append(item)
            #print repr(item).decode("unicode-escape") + '\n'
        return items

注意:

  首行要设置为:#coding=utf-8 或 # -*- coding: utf-8 -*- 哦!否则会报错。

SyntaxError: Non-ASCII character '\xe5' in file /mnt/hgfs/share/cnblogs/cnblogs/spiders/cnblogs_spider.py on line 15, but no encoding declared; see http://python.org/dev/peps/pep-0263/ for details

  spider的名称为:CnblogsSpider,后面会用到。

5、修改pipelines.py文件

[root@bogon cnblogs]# vi cnblogs/pipelines.py

# -*- 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

from scrapy import signals
import json
import codecs
class JsonWithEncodingCnblogsPipeline(object):
    def __init__(self):
        self.file = codecs.open('cnblogs.json', 'w', encoding='utf-8')
    def process_item(self, item, spider):
        line = json.dumps(dict(item), ensure_ascii=False) + "\n"
        self.file.write(line)
        return item
    def spider_closed(self, spider):
        self.file.close()

注意类名为JsonWithEncodingCnblogsPipeline哦!settings.py中会用到

6、修改settings.py,添加以下两个配置项

ITEM_PIPELINES = {
    'cnblogs.pipelines.JsonWithEncodingCnblogsPipeline': 300,
}
LOG_LEVEL = 'INFO'

7、运行spider,scrapy crawl 爬虫名称(cnblogs_spider.py中定义的name)

[root@bogon cnblogs]# scrapy crawl CnblogsSpider

8、查看结果more cnblogs.json(pipelines.py中定义的名称

more cnblogs.json 

9、如果有需要可以将结果转成txt文本格式,可参考另外一篇文章python将json格式的数据转换成文本格式的数据或sql文件

源码可在此下载:https://github.com/jackgitgz/CnblogsSpider

10、相信大家还会有疑问,我们能不能将数据直接保存在数据库呢?答案是可以的,接下来的文章会逐一介绍,敬请期待。

参考资料:

  http://doc.scrapy.org/en/master/

  http://blog.csdn.net/HanTangSongMing/article/details/24454453

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posted @ 2015-06-10 20:04  秋楓  阅读(13611)  评论(6编辑  收藏  举报