『Scrapy』終端調用&選擇器方法
阿新 • • 發佈：2017-08-25
selector 我們 resp 必須 數據結構 tor ipy lec 結合
Scrapy終端
示例，輸入如下命令後shell會進入Python（或IPython）交互式界面：
scrapy shell "http://www.itcast.cn/channel/teacher.shtml"
有一點註意的是必須是雙引號，單引號會報錯。
之後會顯示當前保存的數據結構以供查詢，這和我們編寫py腳本時的數據結構完全相同，可以直接使用相關方法，
諸如：
Scrapy Selectors
如下所示，
>>> response.xpath(‘//title/text()‘)
[<Selector (text) xpath=//title/text()>]
>>> response.css(‘title::text‘)
[<Selector (text) xpath=//title/text()>]
這兩種方式提取的都是節點型數據，所以都可以使用.extract()或者.extract_first()方法提取data部分
以下面的源碼為例進行提取示範：
<html> <head> <base href=‘http://example.com/‘ /> <title>Example website</title> </head> <body> <div id=‘images‘> <a href=‘image1.html‘>Name: My image 1 <br /><img src=‘image1_thumb.jpg‘ /></a> <a href=‘image2.html‘>Name: My image 2 <br /><img src=‘image2_thumb.jpg‘ /></a> <a href=‘image3.html‘>Name: My image 3 <br /><img src=‘image3_thumb.jpg‘ /></a> <a href=‘image4.html‘>Name: My image 4 <br /><img src=‘image4_thumb.jpg‘ /></a> <a href=‘image5.html‘>Name: My image 5 <br /><img src=‘image5_thumb.jpg‘ /></a> </div> </body> </html>
提取標簽屬性，
>>> response.xpath(‘//base/@href‘).extract()
[u‘http://example.com/‘]
>>> response.css(‘base::attr(href)‘).extract()
[u‘http://example.com/‘]
對提取目標路徑的標簽進行篩選，contains(@href, "image")表示href熟悉需要包含image字符，css同理，
response.xpath(‘//a[contains(@href, "image")]/@href‘).extract()
Out[1]: [‘image1.html‘, ‘image2.html‘, ‘image3.html‘, ‘image4.html‘, ‘image5.html‘]
response.xpath(‘//a[contains(@href, "image1")]/@href‘).extract()
Out[2]: [‘image1.html‘]
response.css(‘a[href*=image]::attr(href)‘).extract()
Out[3]: [‘image1.html‘, ‘image2.html‘, ‘image3.html‘, ‘image4.html‘, ‘image5.html‘]
esponse.css(‘a[href*=image2]::attr(href)‘).extract()
Out[4]: [‘image2.html‘]
結合兩者，
>>> response.xpath(‘//a[contains(@href, "image")]/img/@src‘).extract()
[u‘image1_thumb.jpg‘,
u‘image2_thumb.jpg‘,
u‘image3_thumb.jpg‘,
u‘image4_thumb.jpg‘,
u‘image5_thumb.jpg‘]
>>> response.css(‘a[href*=image] img::attr(src)‘).extract()
[u‘image1_thumb.jpg‘,
u‘image2_thumb.jpg‘,
u‘image3_thumb.jpg‘,
u‘image4_thumb.jpg‘,
u‘image5_thumb.jpg‘]
內置了正則表達式re和re_first方法，
response.xpath(‘//a[contains(@href, "image")]/text()‘)
Out[8]:
[<Selector xpath=‘//a[contains(@href, "image")]/text()‘ data=‘Name: My image 1 ‘>,
<Selector xpath=‘//a[contains(@href, "image")]/text()‘ data=‘Name: My image 2 ‘>,
<Selector xpath=‘//a[contains(@href, "image")]/text()‘ data=‘Name: My image 3 ‘>,
<Selector xpath=‘//a[contains(@href, "image")]/text()‘ data=‘Name: My image 4 ‘>,
<Selector xpath=‘//a[contains(@href, "image")]/text()‘ data=‘Name: My image 5 ‘>]
response.xpath(‘//a[contains(@href, "image")]/text()‘).re(r‘Name:\s*(.*)‘)
Out[7]: [‘My image 1 ‘, ‘My image 2 ‘, ‘My image 3 ‘, ‘My image 4 ‘, ‘My image 5 ‘]
response.xpath(‘//a[contains(@href, "image")]/text()‘).re_first(r‘Name:\s*(.*)‘)
Out[9]: ‘My image 1 ‘
『Scrapy』終端調用&選擇器方法