link-extractors.rst

Link Extractors

A link extractor is an object that extracts links from responses.

The __init__ method of ~scrapy.linkextractors.lxmlhtml.LxmlLinkExtractor takes settings that determine which links may be extracted. LxmlLinkExtractor.extract_links <scrapy.linkextractors.lxmlhtml.LxmlLinkExtractor.extract_links> returns a list of matching ~scrapy.link.Link objects from a ~scrapy.http.Response object.

Link extractors are used in ~scrapy.spiders.CrawlSpider spiders through a set of ~scrapy.spiders.Rule objects.

You can also use link extractors in regular spiders. For example, you can instantiate LinkExtractor <scrapy.linkextractors.lxmlhtml.LxmlLinkExtractor> into a class variable in your spider, and use it from your spider callbacks:

def parse(self, response):
    for link in self.link_extractor.extract_links(response):
        yield Request(link.url, callback=self.parse)

Link extractor reference

scrapy.linkextractors

The link extractor class is scrapy.linkextractors.lxmlhtml.LxmlLinkExtractor. For convenience it can also be imported as scrapy.linkextractors.LinkExtractor:

from scrapy.linkextractors import LinkExtractor

LxmlLinkExtractor

scrapy.linkextractors.lxmlhtml

LxmlLinkExtractor is the recommended link extractor with handy filtering options. It is implemented using lxml's robust HTMLParser.

param allow

a single regular expression (or list of regular expressions) that the (absolute) urls must match in order to be extracted. If not given (or empty), it will match all links.

type allow

str or list

param deny

a single regular expression (or list of regular expressions) that the (absolute) urls must match in order to be excluded (i.e. not extracted). It has precedence over the allow parameter. If not given (or empty) it won't exclude any links.

type deny

str or list

param allow_domains

a single value or a list of string containing domains which will be considered for extracting the links

type allow_domains

str or list

param deny_domains

a single value or a list of strings containing domains which won't be considered for extracting the links

type deny_domains

str or list

param deny_extensions

a single value or list of strings containing extensions that should be ignored when extracting links. If not given, it will default to scrapy.linkextractors.IGNORED_EXTENSIONS.

2.0 ~scrapy.linkextractors.IGNORED_EXTENSIONS now includes 7z, 7zip, apk, bz2, cdr, dmg, ico, iso, tar, tar.gz, webm, and xz.

type deny_extensions

list

param restrict_xpaths

is an XPath (or list of XPath's) which defines regions inside the response where links should be extracted from. If given, only the text selected by those XPath will be scanned for links. See examples below.

type restrict_xpaths

str or list

param restrict_css

a CSS selector (or list of selectors) which defines regions inside the response where links should be extracted from. Has the same behaviour as restrict_xpaths.

type restrict_css

str or list

param restrict_text

a single regular expression (or list of regular expressions) that the link's text must match in order to be extracted. If not given (or empty), it will match all links. If a list of regular expressions is given, the link will be extracted if it matches at least one.

type restrict_text

str or list

param tags

a tag or a list of tags to consider when extracting links. Defaults to ('a', 'area').

type tags

str or list

param attrs

an attribute or list of attributes which should be considered when looking for links to extract (only for those tags specified in the tags parameter). Defaults to ('href',)

type attrs

list

param canonicalize

canonicalize each extracted url (using w3lib.url.canonicalize_url). Defaults to False. Note that canonicalize_url is meant for duplicate checking; it can change the URL visible at server side, so the response can be different for requests with canonicalized and raw URLs. If you're using LinkExtractor to follow links it is more robust to keep the default canonicalize=False.

type canonicalize

bool

param unique

whether duplicate filtering should be applied to extracted links.

type unique

bool

param process_value

a function which receives each value extracted from the tag and attributes scanned and can modify the value and return a new one, or return None to ignore the link altogether. If not given, process_value defaults to lambda x: x.

html

For example, to extract links from this code:

<a href="javascript:goToPage('../other/page.html'); return false">Link text</a>

python

You can use the following function in process_value:

def process_value(value):
    m = re.search("javascript:goToPage\('(.*?)'", value)
    if m:
        return m.group(1)

type process_value

collections.abc.Callable

param strip

whether to strip whitespaces from extracted attributes. According to HTML5 standard, leading and trailing whitespaces must be stripped from href attributes of <a>, <area> and many other elements, src attribute of <img>, <iframe> elements, etc., so LinkExtractor strips space chars by default. Set strip=False to turn it off (e.g. if you're extracting urls from elements or attributes which allow leading/trailing whitespaces).

type strip

bool

extract_links

Link

scrapy.link

Link