概览
demo项目步骤
- 创建一个新的Scrapy项目
- 定义索要检索的Item对象
- 编写爬虫并检索Item
- 编写Pipeline存储检索的Item
创建新项目
$scrapy startproject demo
$tree /f
Folder PATH listing
Volume serial number is 24C1-0984
D:.
└─demo
│ scrapy.cfg
│
└─demo
│ items.py
│ pipelines.py
│ settings.py
│ __init__.py
│
└─spiders
__init__.py
文件简介
- scrapy.cfg: 项目配置文件
- demo/: 项目python模块
- demo/items.py: Item文件
- demo/pipelines.py: Pipeline文件
- demo/settings.py: 设置文件
- demo/spiders/: 爬虫目录
定义Item
爬虫的主要目标之一就是从无结构的数据中检索结构的数据。Item是一个简单的容器，包含将要爬取得数据，相当于简单的python字典。
我们将从dmoz.org的页面中获取标题，连接和描述信息。编辑items.py，内容如下：
from scrapy.item import Item, Field
class DmozItem(Item):
title = Field()
link = Field()
desc = Field()
pass
爬
爬虫是用户定义的类，用来从一个或者多个域中获取信息。用户自定义的爬虫需继承scrapy.spider.BaseSpider，有如下几个属性：
- name：唯一的爬虫名字
- start_urls：初始检索页面集
- parse()：downloaded Response对象将调用此方法，负责解析数据，包装成Item对象。
在spider目录下新建dmoz_spider.py，内容如下：
from scrapy.spider import BaseSpider
class DmozSpider(BaseSpider):
name = "dmoz_spider"
allowed_domains = ["dmoz.org"]
start_urls = [
"http://www.dmoz.org/Society/Philosophy/Aesthetics/",
"http://www.dmoz.org/Sports/Football/"
]
def parse(self, response):
filename = response.url.split("/")[-2]
open(filename, 'wb').write(response.body)
运行爬虫命令
$scrapy crawl dmoz_spider
2013-09-05 13:32:01+0800 [scrapy] INFO: Scrapy 0.18.2 started (bot: demo)
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Optional features available: ssl, http11
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Overridden settings: {'NEWSPIDER_MODULE ': 'demo.spiders', 'SPIDER_MODULES': ['demo.spiders'], 'BOT_NAME': 'demo'}
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Enabled extensions: LogStats, TelnetConsole, CloseSpider, WebService, CoreStats, SpiderState
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Enabled item pipelines:
2013-09-05 13:32:01+0800 [dmoz_spider] INFO: Spider opened
2013-09-05 13:32:01+0800 [dmoz_spider] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Telnet console listening on 0.0.0.0:6023
2013-09-05 13:32:01+0800 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
2013-09-05 13:32:02+0800 [dmoz_spider] DEBUG: Crawled (200) <GET http://www.dmoz .org/Sports/Football/> (referer: None)
2013-09-05 13:32:11+0800 [dmoz_spider] DEBUG: Crawled (200) <GET http://www.dmoz .org/Society/Philosophy/Aesthetics/> (referer: None)
2013-09-05 13:32:11+0800 [dmoz_spider] INFO: Closing spider (finished)
2013-09-05 13:32:11+0800 [dmoz_spider] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 482,
'downloader/request_count': 2,
'downloader/request_method_count/GET': 2,
'downloader/response_bytes': 14606,
'downloader/response_count': 2,
'downloader/response_status_count/200': 2,
'finish_reason': 'finished',
'finish_time': datetime.datetime(2013, 9, 5, 5, 32, 11, 220000),
'log_count/DEBUG': 8,
'log_count/INFO': 3,
'response_received_count': 2,
'scheduler/dequeued': 2,
'scheduler/dequeued/memory': 2,
'scheduler/enqueued': 2,
'scheduler/enqueued/memory': 2,
'start_time': datetime.datetime(2013, 9, 5, 5, 32, 1, 560000)}
2013-09-05 13:32:11+0800 [dmoz_spider] INFO: Spider closed (finished)
顶层demo目录下多了两个文件Football/Aesthetics
item检索
Scrapy采用XPath选择器检索数据，一中基于XPath表达式的方式，更多资料查看xpath教程
例如：
/html/head/title: 选择<title>元素
/html/head/title/text(): <title>文本元素
//td: 选择所有的td元素
$scrapy shell http://www.dmoz.org/Computers/Programming/Languages/Python/Books/
2013-09-05 13:56:01+0800 [scrapy] INFO: Scrapy 0.18.2 started (bot: demo)
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Optional features available: ssl, http11
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Overridden settings: {'NEWSPIDER_MODULE': 'demo.spiders', 'SPIDER_MODULES': ['demo.spiders'], 'LOGSTATS_INTERVAL': 0, 'BOT_NAME': 'demo'}
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Enabled extensions: TelnetConsole, CloseSpider, WebService, CoreStats, SpiderState
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Enabled downloader middlewares: HttpAuthMiddleware, DownloadTimeoutMiddleware, UserAgentMiddleware, RetryMiddleware, DefaultHeadersMiddleware, MetaRefreshMiddleware, HttpCompressionMiddleware, RedirectMiddleware, CookiesMiddleware, ChunkedTransferMiddleware, DownloaderStats
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Enabled spider middlewares: HttpErrorMiddleware, OffsiteMiddleware, RefererMiddleware, UrlLengthMiddleware, DepthMiddleware
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Enabled item pipelines:
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Telnet console listening on 0.0.0.0:6023
2013-09-05 13:56:01+0800 [scrapy] DEBUG: Web service listening on 0.0.0.0:6080
2013-09-05 13:56:01+0800 [dmoz_spider] INFO: Spider opened
2013-09-05 13:56:03+0800 [dmoz_spider] DEBUG: Crawled (200) <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Books/> (referer: None)
[s] Available Scrapy objects:
[s] hxs <HtmlXPathSelector xpath=None data=u'<html>\n<head>\n<meta http-equiv="Content-'>
[s] item {}
[s] request <GET http://www.dmoz.org/Computers/Programming/Languages/Python/Books/>
[s] response <200 http://www.dmoz.org/Computers/Programming/Languages/Python/Books/>
[s] settings <CrawlerSettings module=<module 'demo.settings' from 'demo\settings.pyc'>>
[s] spider <DmozSpider 'dmoz_spider' at 0x4bd7e10>
[s] Useful shortcuts:
[s] shelp() Shell help (print this help)
[s] fetch(req_or_url) Fetch request (or URL) and update local objects
[s] view(response) View response in a browser
>>> hxs.select('//title')
[<HtmlXPathSelector xpath='//title' data=u'<title>Open Directory - Computers: Progr'>]
>>> hxs.select('//title').extract()
[u'<title>Open Directory - Computers: Programming: Languages: Python: Books</title>']
>>> hxs.select('//title/text()')
[<HtmlXPathSelector xpath='//title/text()' data=u'Open Directory - Computers: Programming:'>]
>>> hxs.select('//title/text()').extract()
[u'Open Directory - Computers: Programming: Languages: Python: Books']
>>> hxs.select('//title/text()').re('(\w+):')
[u'Computers', u'Programming', u'Languages', u'Python']
>>>
检索存储
将数据存储在我们定义的DmozItem中，修改dmoz_spider.py
from scrapy.spider import BaseSpider
from scrapy.selector import HtmlXPathSelector
from demo.items import DmozItem
class DmozSpider(BaseSpider):
name = "dmoz_spider"
allowed_domains = ["dmoz.org"]
start_urls = [
"http://www.dmoz.org/Society/Philosophy/Aesthetics/",
"http://www.dmoz.org/Sports/Football/"
]
def parse(self, response):
# filename = response.url.split("/")[-2]
# open(filename, 'wb').write(response.body)
hxs = HtmlXPathSelector(response)
sites = hxs.select('//ul/li')
items = []
for site in sites:
item = DmozItem()
item['title'] = site.select('a/text()').extract()
item['link'] = site.select('a/@href').extract()
item['desc'] = site.select('text()').extract()
items.append(item)
return items
运行Scrapy命令，检索的数据将存储在items.json中
scrapy crawl dmoz_spider -o items.json -t json
http://doc.scrapy.org/en/0.18/intro/tutorial.html