我要评论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/',
'http://books.toscrape.com/catalogue/category/books_1/',
'http://books.toscrape.com/catalogue/category/books/travel_2/',
'http://books.toscrape.com/catalogue/category/books/mystery_3/',
'http://books.toscrape.com/catalogue/category/books/historical-fiction_4/',
。。。省略。。。
'http://books.toscrape.com/catalogue/its-only-the-himalayas_981/',
'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/',
'http://books.toscrape.com/catalogue/category/books_1/',
'http://books.toscrape.com/catalogue/a-light-in-the-attic_1000/',
'http://books.toscrape.com/catalogue/tipping-the-velvet_999/',
'http://books.toscrape.com/catalogue/soumission_998/',
'http://books.toscrape.com/catalogue/sharp-objects_997/',
'http://books.toscrape.com/catalogue/sapiens-a-brief-history-of-humankind_996/',
'http://books.toscrape.com/catalogue/the-requiem-red_995/',
'http://books.toscrape.com/catalogue/the-dirty-little-secrets-of-getting-your-dream-job_994/',
'http://books.toscrape.com/catalogue/the-coming-woman-a-novel-based-on-the-life-of-the-infamous-feminist-victoria-woodhull_993/',
'http://books.toscrape.com/catalogue/the-boys-in-the-boat-nine-americans-and-their-epic-quest-for-gold-at-the-1936-berlin-olympics_992/',
'http://books.toscrape.com/catalogue/the-black-maria_991/',
'http://books.toscrape.com/catalogue/starving-hearts-triangular-trade-trilogy-1_990/',
'http://books.toscrape.com/catalogue/shakespeares-sonnets_989/',
'http://books.toscrape.com/catalogue/set-me-free_988/',
'http://books.toscrape.com/catalogue/scott-pilgrims-precious-little-life-scott-pilgrim-1_987/',
'http://books.toscrape.com/catalogue/rip-it-up-and-start-again_986/',
'http://books.toscrape.com/catalogue/our-band-could-be-your-life-scenes-from-the-american-indie-underground-1981-1991_985/',
'http://books.toscrape.com/catalogue/olio_984/',
'http://books.toscrape.com/catalogue/mesaerion-the-best-science-fiction-stories-1800-1849_983/',
'http://books.toscrape.com/catalogue/libertarianism-for-beginners_982/',
'http://books.toscrape.com/catalogue/its-only-the-himalayas_981/',
'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
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