generic extractor (#735)
* Generic extractor, see issue #683 * Fix failed test_names test, no subcategory needed * Prefix directory_fmt with "generic" * Relax regex (would break some urls) * Flake8 compliance * pattern: don't require a scheme This fixes a bug when we force the generic extractor on urls without a scheme (that are allowed by all other extractors). * Fix using g: and r: on urls without http(s) scheme Almost all extractors accept urls without an initial http(s) scheme. Many extractors also allow for generic subdomains in their "pattern" variable; some of them implement this with the regex character class "[^.]+" (everything but a dot). This leads to a problem when the extractor is given a url starting with g: or r: (to force using the generic or recursive extractor) and without the http(s) scheme: e.g. with "r:foobar.tumblr.com" the "r:" is wrongly considered part of the subdomain. This commit fixes the bug, replacing the too generic "[^.]+" with the more specific "[\w-]+" (letters, digits and "-", the only characters allowed in domain names), which is already used by some extractors. * Relax imageurl_pattern_ext: allow relative urls * First round of small suggested changes * Support image urls starting with "//" * self.baseurl: remove trailing slash * Relax regexp (didn't catch some image urls) * Some fixes and cleanup * Fix domain pattern; option to enable extractor Fixed the domain section for "pattern", to pass "test_add" and "test_add_module" tests. Added the "enabled" configuration option (default False) to enable the generic extractor. Using "g(eneric):URL" forces using the extractor.pull/2197/head
Vrihub
3 years ago
committed by
GitHub
parent
4376b39a2b
commit
96fcff182c
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# -*- coding: utf-8 -*-
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"""Extractor for images in a generic web page."""
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from .common import Extractor, Message
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from .. import config, text
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import re
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import os.path
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class GenericExtractor(Extractor):
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"""Extractor for images in a generic web page."""
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category = "generic"
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directory_fmt = ("{category}", "{pageurl}")
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archive_fmt = "{imageurl}"
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# By default, the generic extractor is disabled
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# and the "g(eneric):" prefix in url is required.
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# If the extractor is enabled, make the prefix optional
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pattern = r"(?ix)(?P<generic>g(?:eneric)?:)"
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if config.get(("extractor", "generic"), "enabled"):
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pattern += r"?"
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# The generic extractor pattern should match (almost) any valid url
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# Based on: https://tools.ietf.org/html/rfc3986#appendix-B
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pattern += r"""
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(?P<scheme>https?://)? # optional http(s) scheme
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(?P<domain>[-\w\.]+) # required domain
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(?P<path>/[^?&#]*)? # optional path
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(?:\?(?P<query>[^/?#]*))? # optional query
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(?:\#(?P<fragment>.*))?$ # optional fragment
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"""
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def __init__(self, match):
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"""Init."""
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Extractor.__init__(self, match)
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# Strip the "g(eneric):" prefix
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# and inform about "forced" or "fallback" mode
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if match.group('generic'):
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self.log.info("Forcing use of generic information extractor.")
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self.url = match.group(0).partition(":")[2]
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else:
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self.log.info("Falling back on generic information extractor.")
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self.url = match.group(0)
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# Make sure we have a scheme, or use https
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if match.group('scheme'):
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self.scheme = match.group('scheme')
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else:
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self.scheme = 'https://'
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self.url = self.scheme + self.url
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# Used to resolve relative image urls
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self.root = self.scheme + match.group('domain')
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def items(self):
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"""Get page, extract metadata & images, yield them in suitable messages.
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Adapted from common.GalleryExtractor.items()
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"""
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page = self.request(self.url).text
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data = self.metadata(page)
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imgs = self.images(page)
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try:
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data["count"] = len(imgs)
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except TypeError:
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pass
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images = enumerate(imgs, 1)
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yield Message.Version, 1
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yield Message.Directory, data
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for data["num"], (url, imgdata) in images:
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if imgdata:
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data.update(imgdata)
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if "extension" not in imgdata:
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text.nameext_from_url(url, data)
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else:
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text.nameext_from_url(url, data)
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yield Message.Url, url, data
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def metadata(self, page):
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"""Extract generic webpage metadata, return them in a dict."""
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data = {}
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data['pageurl'] = self.url
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data['title'] = text.extract(page, '<title>', "</title>")[0] or ""
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data['description'] = text.extract(
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page, '<meta name="description" content="', '"')[0] or ""
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data['keywords'] = text.extract(
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page, '<meta name="keywords" content="', '"')[0] or ""
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data['language'] = text.extract(
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page, '<meta name="language" content="', '"')[0] or ""
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data['name'] = text.extract(
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page, '<meta itemprop="name" content="', '"')[0] or ""
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data['copyright'] = text.extract(
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page, '<meta name="copyright" content="', '"')[0] or ""
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data['og_site'] = text.extract(
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page, '<meta property="og:site" content="', '"')[0] or ""
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data['og_site_name'] = text.extract(
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page, '<meta property="og:site_name" content="', '"')[0] or ""
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data['og_title'] = text.extract(
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page, '<meta property="og:title" content="', '"')[0] or ""
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data['og_description'] = text.extract(
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page, '<meta property="og:description" content="', '"')[0] or ""
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data = {k: text.unescape(data[k]) for k in data if data[k] != ""}
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return data
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def images(self, page):
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"""Extract image urls, return a list of (image url, metadata) tuples.
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The extractor aims at finding as many _likely_ image urls as possible,
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using two strategies (see below); since these often overlap, any
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duplicate urls will be removed at the end of the process.
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Note: since we are using re.findall() (see below), it's essential that
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the following patterns contain 0 or at most 1 capturing group, so that
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re.findall() return a list of urls (instead of a list of tuples of
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matching groups). All other groups used in the pattern should be
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non-capturing (?:...).
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1: Look in src/srcset attributes of img/video/source elements
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See:
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https://www.w3schools.com/tags/att_src.asp
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https://www.w3schools.com/tags/att_source_srcset.asp
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We allow both absolute and relative urls here.
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Note that srcset attributes often contain multiple space separated
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image urls; this pattern matches only the first url; remaining urls
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will be matched by the "imageurl_pattern_ext" pattern below.
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"""
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imageurl_pattern_src = r"""(?ix)
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<(?:img|video|source)\s.*? # <img>, <video> or <source>
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src(?:set)?=["']? # src or srcset attributes
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(?P<URL>[^"'\s>]+) # url
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"""
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"""
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2: Look anywhere for urls containing common image/video extensions
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The list of allowed extensions is borrowed from the directlink.py
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extractor; other could be added, see
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https://en.wikipedia.org/wiki/List_of_file_formats
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Compared to the "pattern" class variable, here we must exclude also
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other special characters (space, ", ', >), since we are looking for
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urls in html tags.
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"""
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imageurl_pattern_ext = r"""(?ix)
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(?:[^?&#"'>\s]+) # anything until dot+extension
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\.(?:jpe?g|jpe|png|gif
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|web[mp]|mp4|mkv|og[gmv]|opus) # dot + image/video extensions
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(?:[^"'>\s]*)? # optional query and fragment
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"""
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imageurls_src = re.findall(imageurl_pattern_src, page)
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imageurls_ext = re.findall(imageurl_pattern_ext, page)
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imageurls = imageurls_src + imageurls_ext
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# Resolve relative urls
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#
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# Image urls catched so far may be relative, so we must resolve them
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# by prepending a suitable base url.
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#
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# If the page contains a <base> element, use it as base url
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basematch = re.search(
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r"(?i)(?:<base\s.*?href=[\"']?)(?P<url>[^\"' >]+)", page)
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if basematch:
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self.baseurl = basematch.group('url').rstrip('/')
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# Otherwise, extract the base url from self.url
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else:
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if self.url.endswith("/"):
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self.baseurl = self.url.rstrip('/')
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else:
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self.baseurl = os.path.dirname(self.url)
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# Build the list of absolute image urls
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absimageurls = []
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for u in imageurls:
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# Absolute urls are taken as-is
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if u.startswith('http'):
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absimageurls.append(u)
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# // relative urls are prefixed with current scheme
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elif u.startswith('//'):
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absimageurls.append(self.scheme + u.lstrip('/'))
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# / relative urls are prefixed with current scheme+domain
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elif u.startswith('/'):
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absimageurls.append(self.root + u)
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# other relative urls are prefixed with baseurl
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else:
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absimageurls.append(self.baseurl + '/' + u)
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# Remove duplicates
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absimageurls = set(absimageurls)
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# Create the image metadata dict and add imageurl to it
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# (image filename and extension are added by items())
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images = [(u, {'imageurl': u}) for u in absimageurls]
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return images
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