2014-12-15 09:30:59+0800 [scrapy] INFO: Scrapy 0.24.4 started (bot: tutorial)
2014-12-15 09:30:59+0800 [scrapy] INFO: Optional features available: ssl, http11
2014-12-15 09:30:59+0800 [scrapy] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'tutorial.spiders', 'SPIDER_MODULES': ['tutorial.spiders'], 'BOT_NAME': 'tutorial'}
2014-12-15 09:30:59+0800 [scrapy] INFO: Enabled extensions: LogStats, TelnetConsole, CloseSpider, WebService, CoreStats, SpiderState
2014-12-15 09:30:59+0800 [scrapy] INFO: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2014-12-15 09:30:59+0800 [scrapy] INFO: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2014-12-15 09:30:59+0800 [scrapy] INFO: Enabled item pipelines:
2014-12-15 09:30:59+0800 [dmoz] INFO: Spider opened
2014-12-15 09:30:59+0800 [dmoz] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2014-12-15 09:30:59+0800 [scrapy] DEBUG: Telnet console listening on 127.0.0.1:6023
2014-12-15 09:30:59+0800 [scrapy] DEBUG: Web service listening on 127.0.0.1:6080
2014-12-15 09:31:00+0800 [dmoz] DEBUG: Crawled (200) (referer: None)
2014-12-15 09:31:00+0800 [dmoz] DEBUG: Crawled (200) (referer: None)
2014-12-15 09:31:00+0800 [dmoz] INFO: Closing spider (finished)
2014-12-15 09:31:00+0800 [dmoz] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 516,
'downloader/request_count': 2,
'downloader/request_method_count/GET': 2,
'downloader/response_bytes': 16338,
'downloader/response_count': 2,
'downloader/response_status_count/200': 2,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2014, 12, 15, 1, 31, 0, 666214),
'log_count/DEBUG': 4,
'log_count/INFO': 7,
'response_received_count': 2,
'scheduler/dequeued': 2,
'scheduler/dequeued/memory': 2,
'scheduler/enqueued': 2,
'scheduler/enqueued/memory': 2,
'start_time': datetime.datetime(2014, 12, 15, 1, 30, 59, 533207)}
2014-12-15 09:31:00+0800 [dmoz] INFO: Spider closed (finished)
3.4. 提取Items
3.4.1. 介绍Selector
从网页中提取数据有很多方法。Scrapy使用了一种基于 XPath 或者 CSS 表达式机制： Scrapy Selectors
出XPath表达式的例子及对应的含义:
- /html/head/title: 选择HTML文档中 标签内的 元素</li>
<li>/html/head/title/text(): 选择 <title> 元素内的文本</li>
<li>//td: 选择所有的 <td> 元素</li>
<li>//div[@class="mine"]: 选择所有具有class="mine" 属性的 div 元素</li>
</ul>
<p>等多强大的功能使用可以查看XPath tutorial</p>
<p>为了方便使用 XPaths，Scrapy 提供 Selector 类， 有四种方法 :</p>
<ul>
<li>xpath()：返回selectors列表, 每一个selector表示一个xpath参数表达式选择的节点.</li>
<li>css() : 返回selectors列表, 每一个selector表示CSS参数表达式选择的节点</li>
<li>extract()：返回一个unicode字符串，该字符串为XPath选择器返回的数据</li>
<li>re()： 返回unicode字符串列表，字符串作为参数由正则表达式提取出来</li>
</ul>
<p><strong>3.4.2. 取出数据<br />
</strong></p>
<ul>
<li>首先使用谷歌浏览器开发者工具, 查看网站源码, 来看自己需要取出的数据形式(这种方法比较麻烦), 更简单的方法是直接对感兴趣的东西右键审查元素, 可以直接查看网站源码</li>
</ul>
<p>在查看网站源码后, 网站信息在第二个<ul>内</p>
<div class="jb51code">
<pre class="brush:py;">
<ul class="directory-url" style="margin-left:0;">
<li>Core Python Programming
- By Wesley J. Chun; Prentice Hall PTR, 2001, ISBN 0130260363. For experienced developers to improve extant skills; professional level examples. Starts by introducing syntax, objects, error handling, functions, classes, built-ins. [Prentice Hall]
<div class="flag"><img src="https://www.gxlcms.com/img/flag.png" alt="[!]" title="report an issue with this listing"></div>
</li>
...省略部分...
</ul>
</script></pre>
</p>
<p>那么就可以通过一下方式进行提取数据</p>
<div class="jb51code">
<pre class="brush:py;">
#通过如下命令选择每个在网站中的 <li> 元素:
sel.xpath('//ul/li')
#网站描述:
sel.xpath('//ul/li/text()').extract()
#网站标题:
sel.xpath('//ul/li/a/text()').extract()
#网站链接:
sel.xpath('//ul/li/a/@href').extract()
</script></pre>
</p>
<p>如前所述，每个 xpath() 调用返回一个 selectors 列表，所以我们可以结合 xpath() 去挖掘更深的节点。我们将会用到这些特性，所以:</p>
<div class="jb51code">
<pre class="brush:py;">
for sel in response.xpath('//ul/li')
title = sel.xpath('a/text()').extract()
link = sel.xpath('a/@href').extract()
desc = sel.xpath('text()').extract()
print title, link, desc
</script></pre>
</p>
<p>在已有的爬虫文件中修改代码</p>
<div class="jb51code">
<pre class="brush:py;">
import scrapy
class DmozSpider(scrapy.Spider):
name = "dmoz"
allowed_domains = ["dmoz.org"]
start_urls = [
"http://www.dmoz.org/Computers/Programming/Languages/Python/Books/",
"http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/"
]
def parse(self, response):
for sel in response.xpath('//ul/li'):
title = sel.xpath('a/text()').extract()
link = sel.xpath('a/@href').extract()
desc = sel.xpath('text()').extract()
print title, link, desc
</script></pre>
</p>
<p><strong>3.4.3. 使用item<br />
</strong>Item对象是自定义的python字典,可以使用标准的字典语法来获取到其每个字段的值(字段即是我们之前用Field赋值的属性)</p>
<div class="jb51code">
<pre class="brush:py;">
>>> item = DmozItem()
>>> item['title'] = 'Example title'
>>> item['title']
'Example title'
</script></pre>
</p>
<p>一般来说，Spider将会将爬取到的数据以 Item 对象返回, 最后修改爬虫类，使用 Item 来保存数据，代码如下</p>
<div class="jb51code">
<pre class="brush:py;">
from scrapy.spider import Spider
from scrapy.selector import Selector
from tutorial.items import DmozItem
class DmozSpider(Spider):
name = "dmoz"
allowed_domains = ["dmoz.org"]
start_urls = [
"http://www.dmoz.org/Computers/Programming/Languages/Python/Books/",
"http://www.dmoz.org/Computers/Programming/Languages/Python/Resources/",
]
def parse(self, response):
sel = Selector(response)
sites = sel.xpath('//ul[@class="directory-url"]/li')
items = []
for site in sites:
item = DmozItem()
item['name'] = site.xpath('a/text()').extract()
item['url'] = site.xpath('a/@href').extract()
item['description'] = site.xpath('text()').re('-\s[^\n]*\\r')
items.append(item)
return items
</script></pre>
</p>
<p><strong>3.5. 使用Item Pipeline<br />
</strong>当Item在Spider中被收集之后，它将会被传递到Item Pipeline，一些组件会按照一定的顺序执行对Item的处理。<br />
每个item pipeline组件(有时称之为ItemPipeline)是实现了简单方法的Python类。他们接收到Item并通过它执行一些行为，同时也决定此Item是否继续通过pipeline，或是被丢弃而不再进行处理。<br />
以下是item pipeline的一些典型应用：</p>
<ul>
<li>清理HTML数据</li>
<li>验证爬取的数据(检查item包含某些字段)</li>
<li>查重(并丢弃)</li>
<li>将爬取结果保存，如保存到数据库、XML、JSON等文件中</li>
</ul>
<p>编写你自己的item pipeline很简单，每个item pipeline组件是一个独立的Python类，同时必须实现以下方法:</p>
<p>（1）process_item(item, spider) #每个item pipeline组件都需要调用该方法，这个方法必须返回一个 Item (或任何继承类)对象，或是抛出 DropItem异常，被丢弃的item将不会被之后的pipeline组件所处理。</p>
<p>#参数:</p>
<p>item: 由 parse 方法返回的 Item 对象(Item对象)</p>
<p>spider: 抓取到这个 Item 对象对应的爬虫对象(Spider对象)</p>
<p>（2）open_spider(spider) #当spider被开启时，这个方法被调用。</p>
<p>#参数:</p>
<p>spider : (Spider object) – 被开启的spider</p>
<p>（3）close_spider(spider) #当spider被关闭时，这个方法被调用，可以再爬虫关闭后进行相应的数据处理。</p>
<p>#参数:</p>
<p>spider : (Spider object) – 被关闭的spider</p>
<p>为JSON文件编写一个items</p>
<div class="jb51code">
<pre class="brush:py;">
from scrapy.exceptions import DropItem
class TutorialPipeline(object):
# put all words in lowercase
words_to_filter = ['politics', 'religion']
def process_item(self, item, spider):
for word in self.words_to_filter:
if word in unicode(item['description']).lower():
raise DropItem("Contains forbidden word: %s" % word)
else:
return item
</script></pre>
</p>
<p>在 settings.py 中设置ITEM_PIPELINES激活item pipeline，其默认为[]</p>
<div class="jb51code">
<pre class="brush:py;">
ITEM_PIPELINES = {'tutorial.pipelines.FilterWordsPipeline': 1}
</script></pre>
</p>
<p><strong>3.6. 存储数据<br />
</strong>使用下面的命令存储为json文件格式</p>
<p>scrapy crawl dmoz -o items.json</p>
<p><strong>4.示例<br />
4.1最简单的spider（默认的Spider）<br />
</strong>用实例属性start_urls中的URL构造Request对象<br />
框架负责执行request<br />
将request返回的response对象传递给parse方法做分析</p>
<p>简化后的源码：</p>
<div class="jb51code">
<pre class="brush:py;">
class Spider(object_ref):
"""Base class for scrapy spiders. All spiders must inherit from this
class.
"""
name = None
def __init__(self, name=None, **kwargs):
if name is not None:
self.name = name
elif not getattr(self, 'name', None):
raise ValueError("%s must have a name" % type(self).__name__)
self.__dict__.update(kwargs)
if not hasattr(self, 'start_urls'):
self.start_urls = []
def start_requests(self):
for url in self.start_urls:
yield self.make_requests_from_url(url)
def make_requests_from_url(self, url):
return Request(url, dont_filter=True)
def parse(self, response):
raise NotImplementedError
BaseSpider = create_deprecated_class('BaseSpider', Spider)
</script></pre>
</p>
<p>一个回调函数返回多个request的例子</p>
<div class="jb51code">
<pre class="brush:py;">
import scrapyfrom myproject.items import MyItemclass MySpider(scrapy.Spider):
name = 'example.com'
allowed_domains = ['example.com']
start_urls = [
'http://www.example.com/1.html',
'http://www.example.com/2.html',
'http://www.example.com/3.html',
]
def parse(self, response):
sel = scrapy.Selector(response)
for h3 in response.xpath('//h3').extract():
yield MyItem(title=h3)
for url in response.xpath('//a/@href').extract():
yield scrapy.Request(url, callback=self.parse)
</script></pre>
</p>
<p>构造一个Request对象只需两个参数： URL和回调函数</p>
<p><strong>4.2CrawlSpider<br />
</strong>通常我们需要在spider中决定：哪些网页上的链接需要跟进， 哪些网页到此为止，无需跟进里面的链接。CrawlSpider为我们提供了有用的抽象——Rule，使这类爬取任务变得简单。你只需在rule中告诉scrapy,哪些是需要跟进的。<br />
回忆一下我们爬行mininova网站的spider.</p>
<div class="jb51code">
<pre class="brush:py;">
class MininovaSpider(CrawlSpider):
name = 'mininova'
allowed_domains = ['mininova.org']
start_urls = ['http://www.mininova.org/yesterday']
rules = [Rule(LinkExtractor(allow=['/tor/\d+']), 'parse_torrent')]
def parse_torrent(self, response):
torrent = TorrentItem()
torrent['url'] = response.url
torrent['name'] = response.xpath("//h1/text()").extract()
torrent['description'] = response.xpath("//div[@id='description']").extract()
torrent['size'] = response.xpath("//div[@id='specifications']/p[2]/text()[2]").extract()
return torrent
</script></pre>
</p>
<p>上面代码中 rules的含义是：匹配/tor/\d+的URL返回的内容，交给parse_torrent处理，并且不再跟进response上的URL。<br />
官方文档中也有个例子：</p>
<div class="jb51code">
<pre class="brush:py;">
rules = (
# 提取匹配 'category.php' (但不匹配 'subsection.php') 的链接并跟进链接(没有callback意味着follow默认为True)
Rule(LinkExtractor(allow=('category\.php', ), deny=('subsection\.php', ))),
# 提取匹配 'item.php' 的链接并使用spider的parse_item方法进行分析
Rule(LinkExtractor(allow=('item\.php', )), callback='parse_item'),
)
</script></pre>
</p>
<p>除了Spider和CrawlSpider外，还有XMLFeedSpider, CSVFeedSpider, SitemapSpider </div>
<div class="">
<ul class="m-news-opt fix">
<li class="opt-item">
<a href='/python-357124.html' target='_blank'><p>< 上一篇</p><p class="ellipsis">搭建Python的Django框架环境并建立和运行第一个App的教程</p></a>
</li>
<li class="opt-item ta-r">
<a href='/python-357126.html' target='_blank'><p>下一篇 ></p><p class="ellipsis">Python中shutil模块的常用文件操作函数用法示例</p></a>
</li>
</ul>
</div>
</div>
</div>
<div class="g-title fix">
<h2 class="title-txt">人气教程排行</h2>
</div>
<div class="m-rank u-dashed mb40">
<ul>
<li class="rank-item">
<a href="/python-361871.html" title='对Python2.7pandas中的read_excel详解' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">384次</span>
<span class="g-sort-num top">1</span>
对Python2.7pandas中的read_excel详解 </a>
</li> <li class="rank-item">
<a href="/python-357851.html" title='Python实现定时弹窗提醒' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">383次</span>
<span class="g-sort-num second">2</span>
Python实现定时弹窗提醒 </a>
</li> <li class="rank-item">
<a href="/python-359898.html" title='python爬虫入门（3）--利用requests构建知乎API' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">383次</span>
<span class="g-sort-num third">3</span>
python爬虫入门（3）--利用requests构建知乎API </a>
</li> <li class="rank-item">
<a href="/python-361328.html" title='python如何爬取搜狗微信公众号文章永久链接的思路解析' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">382次</span>
<span class="g-sort-num ">4</span>
python如何爬取搜狗微信公众号文章永久链接的思路解析 </a>
</li> <li class="rank-item">
<a href="/python-363639.html" title='python字典的键可以相同吗' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">381次</span>
<span class="g-sort-num ">5</span>
python字典的键可以相同吗 </a>
</li> <li class="rank-item">
<a href="/python-462846.html" title='python是一种面向什么的语言？' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">381次</span>
<span class="g-sort-num ">6</span>
python是一种面向什么的语言？ </a>
</li> <li class="rank-item">
<a href="/python-355903.html" title='python通过pil为png图片填充上背景颜色的方法' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">381次</span>
<span class="g-sort-num ">7</span>
python通过pil为png图片填充上背景颜色的方法 </a>
</li> <li class="rank-item">
<a href="/python-364233.html" title='python语言的编程模式有什么' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">380次</span>
<span class="g-sort-num ">8</span>
python语言的编程模式有什么 </a>
</li> <li class="rank-item">
<a href="/python-353438.html" title='使用python获取进程pid号的方法' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">380次</span>
<span class="g-sort-num ">9</span>
使用python获取进程pid号的方法 </a>
</li> <li class="rank-item">
<a href="/python-362615.html" title='Python中如何解决无限循环的问题' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">380次</span>
<span class="g-sort-num ">10</span>
Python中如何解决无限循环的问题 </a>
</li> <li class="rank-item">
<a href="/python-466149.html" title='怎么解决pip不是内部或外部命令' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">378次</span>
<span class="g-sort-num ">11</span>
怎么解决pip不是内部或外部命令 </a>
</li> <li class="rank-item">
<a href="/python-374795.html" title='python中def是什么意思' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">378次</span>
<span class="g-sort-num ">12</span>
python中def是什么意思 </a>
</li> <li class="rank-item">
<a href="/python-361381.html" title='对numpy中数组元素的统一赋值实例' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">376次</span>
<span class="g-sort-num ">13</span>
对numpy中数组元素的统一赋值实例 </a>
</li> <li class="rank-item">
<a href="/python-378450.html" title='python的选择语句是什么语句' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">374次</span>
<span class="g-sort-num ">14</span>
python的选择语句是什么语句 </a>
</li> <li class="rank-item">
<a href="/python-362375.html" title='Python中构造方法的解析（附示例）' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">374次</span>
<span class="g-sort-num ">15</span>
Python中构造方法的解析（附示例） </a>
</li> <li class="rank-item">
<a href="/python-360729.html" title='关于python中引入导入与自定义模块以及外部文件的实例分享' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">373次</span>
<span class="g-sort-num ">16</span>
关于python中引入导入与自定义模块以及外部文件的实例分享 </a>
</li> <li class="rank-item">
<a href="/python-364421.html" title='python如何在不同类之间调用方法' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">372次</span>
<span class="g-sort-num ">17</span>
python如何在不同类之间调用方法 </a>
</li> <li class="rank-item">
<a href="/python-462395.html" title='python中的【//】是什么运算符号' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">372次</span>
<span class="g-sort-num ">18</span>
python中的【//】是什么运算符号 </a>
</li> <li class="rank-item">
<a href="/python-363743.html" title='python中╲t是什么' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">371次</span>
<span class="g-sort-num ">19</span>
python中╲t是什么 </a>
</li> <li class="rank-item">
<a href="/python-357501.html" title='python同时给多个变量赋值' class="item-name ellipsis" target="_blank">
<span class="g-art-count fr">371次</span>
<span class="g-sort-num ">20</span>
python同时给多个变量赋值 </a>
</li>
</ul>
</div>
</div>
</div>
<!-- / 教程内容页 -->
</div>
</div>
<!-- 页尾 -->
<div class="footer">
本站所有资源全部来源于网络，若本站发布的内容侵害到您的隐私或者利益，请联系我们删除！</div>
<!-- / 页尾 -->
<script type="text/javascript" src="/kan/js/read.js"></script>
<div style="display:none">
<div class="login-box" id="login-dialog">
<div class="login-top"><a class="current" rel="nofollow" id="login1" onclick="setTab('login',1,2);" >登录</a></div>
<div class="login-form" id="nav-signin">
<!-- <div class="login-ico"><a rel="nofollow" class="qq" id="qqlogin" target="_blank" href="/user-center-qqlogin.html"> QQ </a></div> -->
<div class="login-box-form" id="con_login_1">
<form id="loginform" action="/user-center-login.html" method="post" onsubmit="return false;">
<p class="int-text">
<input class="email" id="username" name="username" type="text" value="用户名或Email" onfocus="if(this.value=='用户名或Email'){this.value='';}" onblur="if(this.value==''){this.value='用户名或Email';};" ></p>
<p class="int-text">
<input class="password1" type="password" id="password" name="password" value="******" onBlur="if(this.value=='') this.value='******';" onFocus="if(this.value=='******') this.value='';" >
</p>
<p class="int-info">
<label class="ui-label"> </label>
<label for="agreement" class="ui-label-checkbox">
<input type="checkbox" value="" name="cookietime" id="cookietime" checked="checked" value="2592000">
<input type="hidden" name="notforward" id="notforward" value="1">
<input type="hidden" name="dosubmit" id="dosubmit" value="1">记住我的登录 </label>
<a rel="nofollow" class="aright" href="/user-center-forgetpwd.html" target="_blank"> 忘记密码？ </a></p>
<p class="int-btn"><a rel="nofollow" id="loginbt" class="loginbtn"><span>登录</span></a></p>
</form>
</div>
<form id="regform" action="/user-center-reg.html" method="post">
<div class="login-reg" style="display: none;" id="con_login_2">
<input type="hidden" name="t" id="t"/>
<p class="int-text">
<input id="email" name="email" type="text" value="Email" onfocus="if(this.value=='Email'){this.value='';}" onblur="if(this.value==''){this.value='Email';};"></p>
<p class="int-text">
<input id="uname" name="username" type="text" value="用户名或昵称" onfocus="if(this.value=='用户名或昵称'){this.value='';}" onblur="if(this.value==''){this.value='用户名或昵称';};"></p>
<p class="int-text">
<input type="password" id="pwd" name="password" value="******" onBlur="if(this.value=='') this.value='******';" onFocus="if(this.value=='******') this.value='';"> </p>
<p class="int-text1"><span class="inputbox">
<input id="validate" name="validate" type="text" value="验证码" onfocus="if(this.value=='验证码'){this.value='';}" onblur="if(this.value==''){this.value='验证码';};">
</span><span class="yzm-img"><img src="/user-checkcode-index" alt="看不清楚换一张" id="indexlogin"></p>
<p class="int-info">
<label>
<input value="" name="agreement" id="agreement" CHECKED="checked" type="checkbox">
我已阅读<a rel="nofollow" href="/user-center-agreement.html">用户协议</a>及<a rel="nofollow" href="/user-center-agreement.html">版权声明</a></label>
</p>
<p class="int-btn"><input type="hidden" name="dosubmit"/>
<a rel="nofollow" class="loginbtn" id="register"><span>注册</span></a></p>
</div>
</form>
</div>
</div>
</div>
</div>
<script type="text/javascript" src="/kan/js/foot_js.js"></script>
<script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "https://hm.baidu.com/hm.js?6dc1c3c5281cf70f49bc0bc860ec24f2";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
<script type="text/javascript" src="/layui/layui.js"></script>
<script>
layui.use('code', function() {
layui.code({
elem: 'pre', //默认值为.layui-code
about: false,
skin: 'notepad',
title: 'php怎么实现数据库验证跳转代码块',
encode: true //是否转义html标签。默认不开启
});
});
</script>
</body>
</html>
