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130 lines
5.3 KiB
Markdown
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如何在Ubuntu 14.04 LTS安装网络爬虫工具
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================================================================================
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这是一款提取网站数据的开源工具。Scrapy框架用Python开发而成，它使抓取工作又快又简单，且可扩展。我们已经在virtual box中创建一台虚拟机（VM）并且在上面安装了Ubuntu 14.04 LTS。
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### 安装 Scrapy ###
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Scrapy依赖于Python、开发库和pip。Python最新的版本已经在Ubuntu上预装了。因此我们在安装Scrapy之前只需安装pip和python开发库就可以了。
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pip是作为python包索引器easy_install的替代品。用于安装和管理Python包。pip包的安装可见图 1。
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sudo apt-get install python-pip
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图:1 pip安装
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我们必须要用下面的命令安装python开发库。如果包没有安装那么就会在安装scrapy框架的时候报关于python.h头文件的错误。
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sudo apt-get install python-dev
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图:2 Python 开发库
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scrapy框架即可从deb包安装也可以从源码安装。然而在图3中我们已经用pip（Python 包管理器）安装了deb包了。
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sudo pip install scrapy
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图:3 Scrapy 安装
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图4中scrapy的成功安装需要一些时间。
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图:4 成功安装Scrapy框架
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### 使用scrapy框架提取数据 ###
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**(基础教程)**
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我们将用scrapy从fatwallet.com上提取店名（提供卡的店）。首先，我们使用下面的命令新建一个scrapy项目“store name”， 见图5。
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$sudo scrapy startproject store_name
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图:5 Scrapy框架新建项目
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Above command creates a directory with title “store_name” at current path. This main directory of the project contains files/folders which are shown in the following Figure 6.
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上面的命令在当前路径创建了一个“store_name”的目录。项目主目录下包含的文件/文件夹见图6。
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$sudo ls –lR store_name
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图:6 store_name项目的内容
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每个文件/文件夹的概要如下：
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- scrapy.cfg 是项目配置文件
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- store_name/ 主目录下的另一个文件夹。 这个目录包含了项目的python代码
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- store_name/items.py 包含了将由蜘蛛爬取的项目
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- store_name/pipelines.py 是管道文件
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- store_name/settings.py 是项目的配置文件
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- store_name/spiders/， 包含了用于爬取的蜘蛛
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由于我们要从fatwallet.com上如提取店名，因此我们如下修改文件。
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import scrapy
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class StoreNameItem(scrapy.Item):
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name = scrapy.Field() # extract the names of Cards store
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之后我们要在项目的store_name/spiders/文件夹下写一个新的蜘蛛。蜘蛛是一个python类，它包含了下面几个必须的属性：
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1. 蜘蛛名 (name )
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2. 爬取起点url (start_urls)
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3. 包含了从响应中提取需要内容相应的正则表达式的解析方法。解析方法对爬虫而言很重要。
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我们在store_name/spiders/目录下创建了“store_name.py”爬虫，并添加如下的代码来从fatwallet.com上提取点名。爬虫的输出到文件（**StoreName.txt**）中，见图7。
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from scrapy.selector import Selector
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from scrapy.spider import BaseSpider
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from scrapy.http import Request
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from scrapy.http import FormRequest
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import re
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class StoreNameItem(BaseSpider):
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name = "storename"
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allowed_domains = ["fatwallet.com"]
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start_urls = ["http://fatwallet.com/cash-back-shopping/"]
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def parse(self,response):
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output = open('StoreName.txt','w')
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resp = Selector(response)
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tags = resp.xpath('//tr[@class="storeListRow"]|\
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//tr[@class="storeListRow even"]|\
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//tr[@class="storeListRow even last"]|\
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//tr[@class="storeListRow last"]').extract()
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for i in tags:
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i = i.encode('utf-8', 'ignore').strip()
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store_name = ''
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if re.search(r"class=\"storeListStoreName\">.*?<",i,re.I|re.S):
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store_name = re.search(r"class=\"storeListStoreName\">.*?<",i,re.I|re.S).group()
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store_name = re.search(r">.*?<",store_name,re.I|re.S).group()
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store_name = re.sub(r'>',"",re.sub(r'<',"",store_name,re.I))
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store_name = re.sub(r'&',"&",re.sub(r'&',"&",store_name,re.I))
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#print store_name
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output.write(store_name+""+"\n")
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图:7 爬虫的输出
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*注意: 本教程的目的仅用于理解scrapy框架*
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--------------------------------------------------------------------------------
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via: http://linoxide.com/ubuntu-how-to/scrapy-install-ubuntu/
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作者：[nido][a]
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译者：[geekpi](https://github.com/geekpi)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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[a]:http://linoxide.com/author/naveeda/
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