scrapy爬虫之LinkExtractor的使用

LinkExtractor

LinkExtractor构造器所有的参数都有默认值，如果构造对象不传参，默认提取页面中所有的链接

2020-07-13 15:24:53 [parso.python.diff] DEBUG: diff parser end
In [1]: from scrapy.linkextractors import LinkExtractor          
                                                     In [2]: le = LinkExtractor()                                     
In [3]: links = le.extract_links(response)                       
In [4]: [link.url for link in links]                             
Out[4]: 
['http://books.toscrape.com/index.html',
 'http://books.toscrape.com/catalogue/category/books_1/index.html',
 'http://books.toscrape.com/catalogue/category/books/travel_2/index.html',
 'http://books.toscrape.com/catalogue/category/books/mystery_3/index.html',
 'http://books.toscrape.com/catalogue/category/books/historical-fiction_4/index.html',
。。。省略。。。
 'http://books.toscrape.com/catalogue/its-only-the-himalayas_981/index.html',
 'http://books.toscrape.com/catalogue/page-2.html']

LinkExtractor中allow参数

接收一个正则表达式或正则表达式列表，提取绝对url与正则匹配的链接，如果该参数为空，提取全部链接

In [21]: from scrapy.linkextractors import LinkExtractor         

In [22]: le = LinkExtractor(allow="/catalogue/page.*\.html$")    

In [23]: links = le.extract_links(response)                      

In [24]: [link.url for link in links]                            
Out[24]: ['http://books.toscrape.com/catalogue/page-2.html']

LinkExtractor中deny参数

接收一个正则表达式或一个正则表达式列表，排除绝对url与正则匹配的链接

In [25]: from scrapy.linkextractors import LinkExtractor         

In [26]: le = LinkExtractor(deny="/catalogue/.*/books/.*")       

In [27]: links = le.extract_links(response)                      

In [28]: [link.url for link in links]                            
Out[28]: 
['http://books.toscrape.com/index.html',
 'http://books.toscrape.com/catalogue/category/books_1/index.html',
 'http://books.toscrape.com/catalogue/a-light-in-the-attic_1000/index.html',
 'http://books.toscrape.com/catalogue/tipping-the-velvet_999/index.html',
 'http://books.toscrape.com/catalogue/soumission_998/index.html',
 'http://books.toscrape.com/catalogue/sharp-objects_997/index.html',
 'http://books.toscrape.com/catalogue/sapiens-a-brief-history-of-humankind_996/index.html',
 'http://books.toscrape.com/catalogue/the-requiem-red_995/index.html',
 'http://books.toscrape.com/catalogue/the-dirty-little-secrets-of-getting-your-dream-job_994/index.html',
 'http://books.toscrape.com/catalogue/the-coming-woman-a-novel-based-on-the-life-of-the-infamous-feminist-victoria-woodhull_993/index.html',
 'http://books.toscrape.com/catalogue/the-boys-in-the-boat-nine-americans-and-their-epic-quest-for-gold-at-the-1936-berlin-olympics_992/index.html',
 'http://books.toscrape.com/catalogue/the-black-maria_991/index.html',
 'http://books.toscrape.com/catalogue/starving-hearts-triangular-trade-trilogy-1_990/index.html',
 'http://books.toscrape.com/catalogue/shakespeares-sonnets_989/index.html',
 'http://books.toscrape.com/catalogue/set-me-free_988/index.html',
 'http://books.toscrape.com/catalogue/scott-pilgrims-precious-little-life-scott-pilgrim-1_987/index.html',
 'http://books.toscrape.com/catalogue/rip-it-up-and-start-again_986/index.html',
 'http://books.toscrape.com/catalogue/our-band-could-be-your-life-scenes-from-the-american-indie-underground-1981-1991_985/index.html',
 'http://books.toscrape.com/catalogue/olio_984/index.html',
 'http://books.toscrape.com/catalogue/mesaerion-the-best-science-fiction-stories-1800-1849_983/index.html',
 'http://books.toscrape.com/catalogue/libertarianism-for-beginners_982/index.html',
 'http://books.toscrape.com/catalogue/its-only-the-himalayas_981/index.html',
 'http://books.toscrape.com/catalogue/page-2.html']

LinkExtractor中allow_domains参数和deny_domains参数

allow_domains：接收一个域名和域名列表，提取指定域名的链接
deny_domains：接收一个域名和域名列表，排除指定域名的链接

#只演示deny_domains
In [29]: from scrapy.linkextractors import LinkExtractor         

In [30]: le = LinkExtractor(deny_domains="books.toscrape.com")   

In [31]: links = le.extract_links(response)                      

In [32]: [link.url for link in links]                            
Out[32]: []

LinkExtractor中restrict_xpaths参数和restrict_css参数

restrict_xpaths：接收一个xpath的表达式，提取表达式选中区域的链接
restrict_css：接收一个css的表达式提取表达式选中区域的链接

#xpaths
In [29]: from scrapy.linkextractors import LinkExtractor         

In [30]: le = LinkExtractor(restrict_xpaths="//li[@class='next']")   

In [31]: links = le.extract_links(response)                    

LinkExtractor中tags参数和attrs参数

tags：接收一个标签或标签列表，提取标签内的列表，默认为[‘a’, ‘area’]
attrs：接收一个属性或属性列表，提取指定属性内的链接，默认为[‘href’]

LinkExtractor中process_value参数

用来回调函数，用来处理JavaScript代码

本文地址：https://blog.csdn.net/fengzhilaoling/article/details/107317870