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"""
Link extractor based on lxml.html
"""
import six
from six.moves.urllib.parse import urljoin
import lxml.etree as etree
from w3lib.html import strip_html5_whitespace
from w3lib.url import canonicalize_url
from scrapy.link import Link
from scrapy.utils.misc import arg_to_iter, rel_has_nofollow
from scrapy.utils.python import unique as unique_list, to_native_str
from scrapy.utils.response import get_base_url
from scrapy.linkextractors import FilteringLinkExtractor
# from lxml/src/lxml/html/__init__.py
XHTML_NAMESPACE = "http://www.w3.org/1999/xhtml"
_collect_string_content = etree.XPath("string()")
def _nons(tag):
if isinstance(tag, six.string_types):
if tag[0] == '{' and tag[1:len(XHTML_NAMESPACE)+1] == XHTML_NAMESPACE:
return tag.split('}')[-1]
return tag
class LxmlParserLinkExtractor(object):
def __init__(self, tag="a", attr="href", process=None, unique=False,
strip=True, canonicalized=False):
self.scan_tag = tag if callable(tag) else lambda t: t == tag
self.scan_attr = attr if callable(attr) else lambda a: a == attr
self.process_attr = process if callable(process) else lambda v: v
self.unique = unique
self.strip = strip
if canonicalized:
self.link_key = lambda link: link.url
else:
self.link_key = lambda link: canonicalize_url(link.url,
keep_fragments=True)
def _iter_links(self, document):
for el in document.iter(etree.Element):
if not self.scan_tag(_nons(el.tag)):
continue
attribs = el.attrib
for attrib in attribs:
if not self.scan_attr(attrib):
continue
yield (el, attrib, attribs[attrib])
def _extract_links(self, selector, response_url, response_encoding, base_url):
links = []
# hacky way to get the underlying lxml parsed document
for el, attr, attr_val in self._iter_links(selector.root):
# pseudo lxml.html.HtmlElement.make_links_absolute(base_url)
try:
if self.strip:
attr_val = strip_html5_whitespace(attr_val)
attr_val = urljoin(base_url, attr_val)
except ValueError:
continue # skipping bogus links
else:
url = self.process_attr(attr_val)
if url is None:
continue
url = to_native_str(url, encoding=response_encoding)
# to fix relative links after process_value
url = urljoin(response_url, url)
link = Link(url, _collect_string_content(el) or u'',
nofollow=rel_has_nofollow(el.get('rel')))
links.append(link)
return self._deduplicate_if_needed(links)
def extract_links(self, response):
base_url = get_base_url(response)
return self._extract_links(response.selector, response.url, response.encoding, base_url)
def _process_links(self, links):
""" Normalize and filter extracted links
The subclass should override it if neccessary
"""
return self._deduplicate_if_needed(links)
def _deduplicate_if_needed(self, links):
if self.unique:
return unique_list(links, key=self.link_key)
return links
class LxmlLinkExtractor(FilteringLinkExtractor):
def __init__(self, allow=(), deny=(), allow_domains=(), deny_domains=(), restrict_xpaths=(),
tags=('a', 'area'), attrs=('href',), canonicalize=False,
unique=True, process_value=None, deny_extensions=None, restrict_css=(),
strip=True):
tags, attrs = set(arg_to_iter(tags)), set(arg_to_iter(attrs))
tag_func = lambda x: x in tags
attr_func = lambda x: x in attrs
lx = LxmlParserLinkExtractor(
tag=tag_func,
attr=attr_func,
unique=unique,
process=process_value,
strip=strip,
canonicalized=canonicalize
)
super(LxmlLinkExtractor, self).__init__(lx, allow=allow, deny=deny,
allow_domains=allow_domains, deny_domains=deny_domains,
restrict_xpaths=restrict_xpaths, restrict_css=restrict_css,
canonicalize=canonicalize, deny_extensions=deny_extensions)
def extract_links(self, response):
base_url = get_base_url(response)
if self.restrict_xpaths:
docs = [subdoc
for x in self.restrict_xpaths
for subdoc in response.xpath(x)]
else:
docs = [response.selector]
all_links = []
for doc in docs:
links = self._extract_links(doc, response.url, response.encoding, base_url)
all_links.extend(self._process_links(links))
return unique_list(all_links)
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