Spider开发流程——用Item封装选中的数据

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Item是一个基类,用于封装数据,与C++的结构体的功能类似,也是把许多不同类型的数据封装起来。并且由于Item是一个类,支持实例化,支持继承,并且可以通过无限制继承来不断根据需要创建自己需要的类型。
在scrapy中,只需要在itens.py文件中写入自己想加入的类,或者说把爬取到的数据封装成什么类型,使用到Field()模块。
class PractiseItem(Item):
    address=Field()
    alternative=Field()
这里添加了两个字段,一个是“address”,一个是“alternative”。
接着只要重写parser函数就可以:
def parse(self,response):
    # 提取数据
    for selector in response.xpath('/html/body/div/a'):
        practise=PractiseItem()
        practise['address']=selector.xpath('./@href').extract_first()
        practise['alternative']=selector.xpath('./img/@alt').extract_first()
        yield practise
<!DOCTYPE html>
<html>
	<head>
		<base href="http://www.baidu.com/">
		<meta charset="utf-8">
		<title>book Spider example</title>
	</head>
	<body>
		<div id='images'>
			<a href="pic1/">图片1<br/><img src="./img/6baa0c32b53eb98abb3d8e40e7444257.jpg" alt="picture lost"></a>
			<br>
			<a href="pic2/">图片2<br/><img src="./img/webp.webp" alt="picture lost"></a>
			<br>
			<a href="pic3/">图片3<br/><img src="./img/未标题-1.jpg" alt="picture lost"></a>
			<br>
			<a href="pic4">图片4<br><img src="./img/背景.jpg" alt="picture lost"></a>
		</div>
	</body>
</html>
这是待爬取的网页的html文档。

继承Spider类之后:

#-*-coding:utf-8 -*-
import scrapy
from ..items import PractiseItem
class BookSpider(scrapy.Spider):
    name = 'practise'
    start_urls=['http://127.0.0.1:8848/%E7%AC%AC%E4%B8%80%E4%B8%AAhtml%E9%A1%B9%E7%9B%AE/index.html']
    def parse(self,response):
        # 提取数据
        for selector in response.xpath('/html/body/div/a'):
            practise=PractiseItem()
            practise['address']=selector.xpath('./@href').extract_first()
            practise['alternative']=selector.xpath('./img/@alt').extract_first()
            yield practise
然后在命令行运行Spider:
PS C:\Users\18813421705xbx\text> scrapy crawl practise -o practise.csv
2020-09-10 19:58:24 [scrapy.utils.log] INFO: Scrapy 2.3.0 started (bot: text)
2020-09-10 19:58:24 [scrapy.utils.log] INFO: Versions: lxml 4.5.2.0, libxml2 2.9.5, cssselect 1.1.0, parsel 1.6.0, w3lib 1.20.0, Twisted 20.3.0, Python 3.8.2 (tags/v3.8.2:7b3ab59, Feb 25 2020, 23:03:10) [MSC v.1916 64 bit (AMD64)], pyOpenSSL 19.1.0 (OpenSSL 1.1.1g  21 Apr 2020), cryptography 3.1, Platform Windows-10-10.0.18362-SP0
2020-09-10 19:58:24 [scrapy.utils.log] DEBUG: Using reactor: twisted.internet.selectreactor.SelectReactor
2020-09-10 19:58:24 [scrapy.crawler] INFO: Overridden settings:
{'BOT_NAME': 'text',
 'NEWSPIDER_MODULE': 'text.spiders',
 'ROBOTSTXT_OBEY': True,
 'SPIDER_MODULES': ['text.spiders']}
2020-09-10 19:58:24 [scrapy.extensions.telnet] INFO: Telnet Password: eddaecdfa02c7270
2020-09-10 19:58:24 [scrapy.middleware] INFO: Enabled extensions:
['scrapy.extensions.corestats.CoreStats',
 'scrapy.extensions.telnet.TelnetConsole',
 'scrapy.extensions.feedexport.FeedExporter',
 'scrapy.extensions.logstats.LogStats']
2020-09-10 19:58:24 [scrapy.middleware] INFO: Enabled downloader middlewares:
['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
 'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
 'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
 'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
 'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
 'scrapy.downloadermiddlewares.retry.RetryMiddleware',
 'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
 'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
 'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
 'scrapy.downloadermiddlewares.httpproxy.HttpProxyMiddleware',
 'scrapy.downloadermiddlewares.stats.DownloaderStats']
2020-09-10 19:58:24 [scrapy.middleware] INFO: Enabled spider middlewares:
['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
 'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
 'scrapy.spidermiddlewares.referer.RefererMiddleware',
 'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
 'scrapy.spidermiddlewares.depth.DepthMiddleware']
2020-09-10 19:58:24 [scrapy.middleware] INFO: Enabled item pipelines:
[]
2020-09-10 19:58:24 [scrapy.core.engine] INFO: Spider opened
2020-09-10 19:58:24 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
2020-09-10 19:58:24 [scrapy.extensions.telnet] INFO: Telnet console listening on 127.0.0.1:6023
2020-09-10 19:58:24 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://127.0.0.1:8848/robots.txt> (referer: None)
2020-09-10 19:58:24 [protego] DEBUG: Rule at line 9 without any user agent to enforce it on.
2020-09-10 19:58:24 [protego] DEBUG: Rule at line 10 without any user agent to enforce it on.
2020-09-10 19:58:24 [protego] DEBUG: Rule at line 11 without any user agent to enforce it on.
2020-09-10 19:58:24 [protego] DEBUG: Rule at line 14 without any user agent to enforce it on.
2020-09-10 19:58:24 [scrapy.core.engine] DEBUG: Crawled (200) <GET http://127.0.0.1:8848/%E7%AC%AC%E4%B8%80%E4%B8%AAhtml%E9%A1%B9%E7%9B%AE/index.html> (referer: None)
2020-09-10 19:58:24 [scrapy.core.scraper] DEBUG: Scraped from <200 http://127.0.0.1:8848/%E7%AC%AC%E4%B8%80%E4%B8%AAhtml%E9%A1%B9%E7%9B%AE/index.html>
{'address': 'pic1/', 'alternative': 'picture lost'}
2020-09-10 19:58:24 [scrapy.core.scraper] DEBUG: Scraped from <200 http://127.0.0.1:8848/%E7%AC%AC%E4%B8%80%E4%B8%AAhtml%E9%A1%B9%E7%9B%AE/index.html>
{'address': 'pic2/', 'alternative': 'picture lost'}
2020-09-10 19:58:24 [scrapy.core.scraper] DEBUG: Scraped from <200 http://127.0.0.1:8848/%E7%AC%AC%E4%B8%80%E4%B8%AAhtml%E9%A1%B9%E7%9B%AE/index.html>
{'address': 'pic3/', 'alternative': 'picture lost'}
2020-09-10 19:58:24 [scrapy.core.scraper] DEBUG: Scraped from <200 http://127.0.0.1:8848/%E7%AC%AC%E4%B8%80%E4%B8%AAhtml%E9%A1%B9%E7%9B%AE/index.html>
{'address': 'pic4', 'alternative': 'picture lost'}
2020-09-10 19:58:24 [scrapy.core.engine] INFO: Closing spider (finished)
2020-09-10 19:58:24 [scrapy.extensions.feedexport] INFO: Stored csv feed (4 items) in: practise.csv
2020-09-10 19:58:24 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
{'downloader/request_bytes': 488,
 'downloader/request_count': 2,
 'downloader/request_method_count/GET': 2,
 'downloader/response_bytes': 2272,
 'downloader/response_count': 2,
 'downloader/response_status_count/200': 2,
 'elapsed_time_seconds': 0.139461,
 'finish_reason': 'finished',
 'finish_time': datetime.datetime(2020, 9, 10, 11, 58, 24, 912071),
 'item_scraped_count': 4,
 'log_count/DEBUG': 10,
 'log_count/INFO': 11,
 'response_received_count': 2,
 'robotstxt/request_count': 1,
 'robotstxt/response_count': 1,
 'robotstxt/response_status_count/200': 1,
 'scheduler/dequeued': 1,
 'scheduler/dequeued/memory': 1,
 'scheduler/enqueued': 1,
 'scheduler/enqueued/memory': 1,
 'start_time': datetime.datetime(2020, 9, 10, 11, 58, 24, 772610)}
2020-09-10 19:58:24 [scrapy.core.engine] INFO: Spider closed (finished)
在爬虫工程存放文件夹里看到存储好的csv文件:

打开文件:

已经爬取到我们想要的数据了。