一、实验环境

1.Windows7x64_SP1

2.anaconda3 + python3.7.3(anaconda集成，不需单独安装)

3.scrapy1.6.0

二、用法举例

1.开启scrapy shell，在命令行输入如下命令：

scrapy shell http://doc.scrapy.org/en/latest/_static/selectors-sample1.html

结果如下：

2.提取a节点

• xpath中用法

result = response.xpath(‘//a‘)

结果如下：

[<Selector xpath=‘//a‘ data=‘<a href="image1.html">Name: My image 1 <‘>,
 <Selector xpath=‘//a‘ data=‘<a href="image2.html">Name: My image 2 <‘>,
 <Selector xpath=‘//a‘ data=‘<a href="image3.html">Name: My image 3 <‘>,
 <Selector xpath=‘//a‘ data=‘<a href="image4.html">Name: My image 4 <‘>,
 <Selector xpath=‘//a‘ data=‘<a href="image5.html">Name: My image 5 <‘>]

• css中用法

result = response.css(‘a‘)

结果如下：

[<Selector xpath=‘descendant-or-self::a‘ data=‘<a href="image1.html">Name: My image 1 <‘>,
 <Selector xpath=‘descendant-or-self::a‘ data=‘<a href="image2.html">Name: My image 2 <‘>,
 <Selector xpath=‘descendant-or-self::a‘ data=‘<a href="image3.html">Name: My image 3 <‘>,
 <Selector xpath=‘descendant-or-self::a‘ data=‘<a href="image4.html">Name: My image 4 <‘>,
 <Selector xpath=‘descendant-or-self::a‘ data=‘<a href="image5.html">Name: My image 5 <‘>]

3.查看result的类型

 type(result)

结果如下：

scrapy.selector.unified.SelectorList

说明：result为Selector组成的列表，也是SelectList类型，他们都可以继续调用xpath()和css()等方法，进一步提取数据。

4.查看result提取数据全部内容，使用extract()函数

result.extract()　　

结果如下：

[‘<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>‘]

5.提取节点内容

• xpath中用法，使用text()函数

response.xpath(‘//a/text()‘)

结果如下：

[<Selector xpath=‘//a/text()‘ data=‘Name: My image 1 ‘>,
 <Selector xpath=‘//a/text()‘ data=‘Name: My image 2 ‘>,
 <Selector xpath=‘//a/text()‘ data=‘Name: My image 3 ‘>,
 <Selector xpath=‘//a/text()‘ data=‘Name: My image 4 ‘>,
 <Selector xpath=‘//a/text()‘ data=‘Name: My image 5 ‘>]

查看HTML内容

response.xpath(‘//a/text()‘).extract()

结果如下：

[‘Name: My image 1 ‘,
 ‘Name: My image 2 ‘,
 ‘Name: My image 3 ‘,
 ‘Name: My image 4 ‘,
 ‘Name: My image 5 ‘]

• css中用法

response.css(‘a::text‘).extract()

结果如下：

[‘Name: My image 1 ‘,
 ‘Name: My image 2 ‘,
 ‘Name: My image 3 ‘,
 ‘Name: My image 4 ‘,
 ‘Name: My image 5 ‘]

6.提取属性值

• xpath中用法，使用/@属性名（如/@href）

response.xpath(‘//a/@href‘).extract()

结果如下：

[‘image1.html‘, ‘image2.html‘, ‘image3.html‘, ‘image4.html‘, ‘image5.html‘]

• css中用法

response.css(‘a::attr("href")‘).extract()

结果如下：

[‘image1.html‘, ‘image2.html‘, ‘image3.html‘, ‘image4.html‘, ‘image5.html‘]　

7.提取节点内部子节点

• xpath中用法，/子节点名　　

response.xpath(‘//a/img‘).extract()

结果如下：

[‘<img src="image1_thumb.jpg">‘,
 ‘<img src="image2_thumb.jpg">‘,
 ‘<img src="image3_thumb.jpg">‘,
 ‘<img src="image4_thumb.jpg">‘,
 ‘<img src="image5_thumb.jpg">‘]

• css中用法

response.css(‘a img‘).extract()

结果如下：

[‘<img src="image1_thumb.jpg">‘,
 ‘<img src="image2_thumb.jpg">‘,
 ‘<img src="image3_thumb.jpg">‘,
 ‘<img src="image4_thumb.jpg">‘,
 ‘<img src="image5_thumb.jpg">‘]

再提取其中的src属性值，与步骤6相同

• xpath用法

response.xpath(‘//a/img/@src‘).extract()

• css用法

response.css(‘a img::attr("src")‘).extract()

8.公用方法

• extract_first()　　#用于提取第一个元素
• extract_first(‘default value‘) 　　#同上，添加默认参数

原文地址：https://www.cnblogs.com/hester/p/11371384.html