python-readability/readability/readability.py

#!/usr/bin/env python
import logging
import re
import sys

from collections import defaultdict
from lxml.etree import tostring
from lxml.etree import tounicode
from lxml.html import document_fromstring
from lxml.html import fragment_fromstring

from cleaners import clean_attributes
from cleaners import html_cleaner
from htmls import build_doc
from htmls import get_body
from htmls import get_title
from htmls import shorten_title


logging.basicConfig(level=logging.INFO)
log = logging.getLogger()


REGEXES = {
    'unlikelyCandidatesRe': re.compile('combx|comment|community|disqus|extra|foot|header|menu|remark|rss|shoutbox|sidebar|sponsor|ad-break|agegate|pagination|pager|popup|tweet|twitter', re.I),
    'okMaybeItsACandidateRe': re.compile('and|article|body|column|main|shadow', re.I),
    'positiveRe': re.compile('article|body|content|entry|hentry|main|page|pagination|post|text|blog|story', re.I),
    'negativeRe': re.compile('combx|comment|com-|contact|foot|footer|footnote|masthead|media|meta|outbrain|promo|related|scroll|shoutbox|sidebar|sponsor|shopping|tags|tool|widget', re.I),
    'divToPElementsRe': re.compile('<(a|blockquote|dl|div|img|ol|p|pre|table|ul)', re.I),
    #'replaceBrsRe': re.compile('(<br[^>]*>[ \n\r\t]*){2,}',re.I),
    #'replaceFontsRe': re.compile('<(\/?)font[^>]*>',re.I),
    #'trimRe': re.compile('^\s+|\s+$/'),
    #'normalizeRe': re.compile('\s{2,}/'),
    #'killBreaksRe': re.compile('(<br\s*\/?>(\s|&nbsp;?)*){1,}/'),
    #'videoRe': re.compile('http:\/\/(www\.)?(youtube|vimeo)\.com', re.I),
    #skipFootnoteLink:      /^\s*(\[?[a-z0-9]{1,2}\]?|^|edit|citation needed)\s*$/i,
}


class Unparseable(ValueError):
    pass


def describe(node, depth=1):
    if not hasattr(node, 'tag'):
        return "[%s]" % type(node)
    name = node.tag
    if node.get('id', ''):
        name += '#' + node.get('id')
    if node.get('class', ''):
        name += '.' + node.get('class').replace(' ', '.')
    if name[:4] in ['div#', 'div.']:
        name = name[3:]
    if depth and node.getparent() is not None:
        return name + ' - ' + describe(node.getparent(), depth - 1)
    return name


def to_int(x):
    if not x:
        return None
    x = x.strip()
    if x.endswith('px'):
        return int(x[:-2])
    if x.endswith('em'):
        return int(x[:-2]) * 12
    return int(x)


def clean(text):
    text = re.sub('\s*\n\s*', '\n', text)
    text = re.sub('[ \t]{2,}', ' ', text)
    return text.strip()


def text_length(i):
    return len(clean(i.text_content() or ""))


class Document:
    """Class to build a etree document out of html."""
    TEXT_LENGTH_THRESHOLD = 25
    RETRY_LENGTH = 250

    def __init__(self, input, **options):
        """Generate the document

        :param input: string of the html content.

        kwargs:
            - attributes:
            - debug: output debug messages
            - min_text_length:
            - retry_length:
            - url: will allow adjusting links to be absolute

        """
        self.input = input
        self.options = options
        self.html = None

    def _html(self, force=False):
        if force or self.html is None:
            self.html = self._parse(self.input)
        return self.html

    def _parse(self, input):
        doc = build_doc(input)
        doc = html_cleaner.clean_html(doc)
        base_href = self.options.get('url', None)
        if base_href:
            doc.make_links_absolute(base_href, resolve_base_href=True)
        else:
            doc.resolve_base_href()
        return doc

    def content(self):
        return get_body(self._html(True))

    def title(self):
        return get_title(self._html(True))

    def short_title(self):
        return shorten_title(self._html(True))

    def summary(self, document_only=False):
        """Generate the summary of the html docuemnt

        :param document_only: return only the div of the document, don't wrap
        in html and body tags.

        """
        try:
            ruthless = True
            while True:
                self._html(True)
                for i in self.tags(self.html, 'script', 'style'):
                    i.drop_tree()
                for i in self.tags(self.html, 'body'):
                    i.set('id', 'readabilityBody')
                if ruthless:
                    self.remove_unlikely_candidates()
                self.transform_misused_divs_into_paragraphs()
                candidates = self.score_paragraphs()

                best_candidate = self.select_best_candidate(candidates)

                if best_candidate:
                    article = self.get_article(candidates, best_candidate,
                            document_only=document_only)
                else:
                    if ruthless:
                        log.debug("ruthless removal did not work. ")
                        ruthless = False
                        self.debug(
                            ("ended up stripping too much - "
                             "going for a safer _parse"))
                        # try again
                        continue
                    else:
                        log.debug(
                            ("Ruthless and lenient parsing did not work. "
                             "Returning raw html"))
                        article = self.html.find('body')
                        if article is None:
                            article = self.html
                cleaned_article = self.sanitize(article, candidates)
                article_length = len(cleaned_article or '')
                retry_length = self.options.get(
                    'retry_length',
                    self.RETRY_LENGTH)
                of_acceptable_length = article_length >= retry_length
                if ruthless and not of_acceptable_length:
                    ruthless = False
                    # Loop through and try again.
                    continue
                else:
                    return cleaned_article
        except StandardError, e:
            log.exception('error getting summary: ')
            raise Unparseable(str(e)), None, sys.exc_info()[2]

    def get_article(self, candidates, best_candidate, document_only=False):
        # Now that we have the top candidate, look through its siblings for
        # content that might also be related.
        # Things like preambles, content split by ads that we removed, etc.
        sibling_score_threshold = max([
            10,
            best_candidate['content_score'] * 0.2])
        # create a new html document with a html->body->div
        if document_only:
            output = fragment_fromstring('<div/>')
        else:
            output = document_fromstring('<div/>')
        best_elem = best_candidate['elem']
        for sibling in best_elem.getparent().getchildren():
            # in lxml there no concept of simple text
            # if isinstance(sibling, NavigableString): continue
            append = False
            if sibling is best_elem:
                append = True
            sibling_key = sibling  # HashableElement(sibling)
            if sibling_key in candidates and \
                candidates[sibling_key]['content_score'] >= sibling_score_threshold:
                append = True

            if sibling.tag == "p":
                link_density = self.get_link_density(sibling)
                node_content = sibling.text or ""
                node_length = len(node_content)

                if node_length > 80 and link_density < 0.25:
                    append = True
                elif node_length <= 80 \
                    and link_density == 0 \
                    and re.search('\.( |$)', node_content):
                    append = True

            if append:
                # We don't want to append directly to output, but the div
                # in html->body->div
                if document_only:
                    output.append(sibling)
                else:
                    output.getchildren()[0].getchildren()[0].append(sibling)
        #if output is not None:
        #    output.append(best_elem)
        return output

    def select_best_candidate(self, candidates):
        sorted_candidates = sorted(candidates.values(), key=lambda x: x['content_score'], reverse=True)
        for candidate in sorted_candidates[:5]:
            elem = candidate['elem']
            self.debug("Top 5 : %6.3f %s" % (
                candidate['content_score'],
                describe(elem)))

        if len(sorted_candidates) == 0:
            return None

        best_candidate = sorted_candidates[0]
        return best_candidate

    def get_link_density(self, elem):
        link_length = 0
        for i in elem.findall(".//a"):
            link_length += text_length(i)
        #if len(elem.findall(".//div") or elem.findall(".//p")):
        #    link_length = link_length
        total_length = text_length(elem)
        return float(link_length) / max(total_length, 1)

    def score_paragraphs(self, ):
        MIN_LEN = self.options.get(
            'min_text_length',
            self.TEXT_LENGTH_THRESHOLD)
        candidates = {}
        ordered = []
        for elem in self.tags(self._html(), "p", "pre", "td"):
            parent_node = elem.getparent()
            if parent_node is None:
                continue
            grand_parent_node = parent_node.getparent()

            inner_text = clean(elem.text_content() or "")
            inner_text_len = len(inner_text)

            # If this paragraph is less than 25 characters
            # don't even count it.
            if inner_text_len < MIN_LEN:
                continue

            if parent_node not in candidates:
                candidates[parent_node] = self.score_node(parent_node)
                ordered.append(parent_node)

            if grand_parent_node is not None and grand_parent_node not in candidates:
                candidates[grand_parent_node] = self.score_node(
                    grand_parent_node)
                ordered.append(grand_parent_node)

            content_score = 1
            content_score += len(inner_text.split(','))
            content_score += min((inner_text_len / 100), 3)
            #if elem not in candidates:
            #    candidates[elem] = self.score_node(elem)

            #WTF? candidates[elem]['content_score'] += content_score
            candidates[parent_node]['content_score'] += content_score
            if grand_parent_node is not None:
                candidates[grand_parent_node]['content_score'] += content_score / 2.0

        # Scale the final candidates score based on link density. Good content
        # should have a relatively small link density (5% or less) and be
        # mostly unaffected by this operation.
        for elem in ordered:
            candidate = candidates[elem]
            ld = self.get_link_density(elem)
            score = candidate['content_score']
            self.debug("Candid: %6.3f %s link density %.3f -> %6.3f" % (
                score,
                describe(elem),
                ld,
                score * (1 - ld)))
            candidate['content_score'] *= (1 - ld)

        return candidates

    def class_weight(self, e):
        weight = 0
        if e.get('class', None):
            if REGEXES['negativeRe'].search(e.get('class')):
                weight -= 25

            if REGEXES['positiveRe'].search(e.get('class')):
                weight += 25

        if e.get('id', None):
            if REGEXES['negativeRe'].search(e.get('id')):
                weight -= 25

            if REGEXES['positiveRe'].search(e.get('id')):
                weight += 25

        return weight

    def score_node(self, elem):
        content_score = self.class_weight(elem)
        name = elem.tag.lower()
        if name == "div":
            content_score += 5
        elif name in ["pre", "td", "blockquote"]:
            content_score += 3
        elif name in ["address", "ol", "ul", "dl", "dd", "dt", "li", "form"]:
            content_score -= 3
        elif name in ["h1", "h2", "h3", "h4", "h5", "h6", "th"]:
            content_score -= 5
        return {
            'content_score': content_score,
            'elem': elem
        }

    def debug(self, *a):
        if self.options.get('debug', False):
            log.debug(*a)

    def remove_unlikely_candidates(self):
        for elem in self.html.iter():
            s = "%s %s" % (elem.get('class', ''), elem.get('id', ''))
            if len(s) < 2:
                continue
            #self.debug(s)
            if REGEXES['unlikelyCandidatesRe'].search(s) and (not REGEXES['okMaybeItsACandidateRe'].search(s)) and elem.tag != 'body':
                self.debug("Removing unlikely candidate - %s" % describe(elem))
                elem.drop_tree()

    def transform_misused_divs_into_paragraphs(self):
        for elem in self.tags(self.html, 'div'):
            # transform <div>s that do not contain other block elements into
            # <p>s
            #FIXME: The current implementation ignores all descendants that
            # are not direct children of elem
            # This results in incorrect results in case there is an <img>
            # buried within an <a> for example
            if not REGEXES['divToPElementsRe'].search(
                    unicode(''.join(map(tostring, list(elem))))):
                #self.debug("Altering %s to p" % (describe(elem)))
                elem.tag = "p"
                #print "Fixed element "+describe(elem)

        for elem in self.tags(self.html, 'div'):
            if elem.text and elem.text.strip():
                p = fragment_fromstring('<p/>')
                p.text = elem.text
                elem.text = None
                elem.insert(0, p)
                #print "Appended "+tounicode(p)+" to "+describe(elem)

            for pos, child in reversed(list(enumerate(elem))):
                if child.tail and child.tail.strip():
                    p = fragment_fromstring('<p/>')
                    p.text = child.tail
                    child.tail = None
                    elem.insert(pos + 1, p)
                    #print "Inserted "+tounicode(p)+" to "+describe(elem)
                if child.tag == 'br':
                    #print 'Dropped <br> at '+describe(elem)
                    child.drop_tree()

    def tags(self, node, *tag_names):
        for tag_name in tag_names:
            for e in node.findall('.//%s' % tag_name):
                yield e

    def reverse_tags(self, node, *tag_names):
        for tag_name in tag_names:
            for e in reversed(node.findall('.//%s' % tag_name)):
                yield e

    def sanitize(self, node, candidates):
        MIN_LEN = self.options.get('min_text_length',
            self.TEXT_LENGTH_THRESHOLD)
        for header in self.tags(node, "h1", "h2", "h3", "h4", "h5", "h6"):
            if self.class_weight(header) < 0 or self.get_link_density(header) > 0.33:
                header.drop_tree()

        for elem in self.tags(node, "form", "iframe", "textarea"):
            elem.drop_tree()
        allowed = {}
        # Conditionally clean <table>s, <ul>s, and <div>s
        for el in self.reverse_tags(node, "table", "ul", "div"):
            if el in allowed:
                continue
            weight = self.class_weight(el)
            if el in candidates:
                content_score = candidates[el]['content_score']
                #print '!',el, '-> %6.3f' % content_score
            else:
                content_score = 0
            tag = el.tag

            if weight + content_score < 0:
                self.debug("Cleaned %s with score %6.3f and weight %-3s" %
                    (describe(el), content_score, weight, ))
                el.drop_tree()
            elif el.text_content().count(",") < 10:
                counts = {}
                for kind in ['p', 'img', 'li', 'a', 'embed', 'input']:
                    counts[kind] = len(el.findall('.//%s' % kind))
                counts["li"] -= 100

                # Count the text length excluding any surrounding whitespace
                content_length = text_length(el)
                link_density = self.get_link_density(el)
                parent_node = el.getparent()
                if parent_node is not None:
                    if parent_node in candidates:
                        content_score = candidates[parent_node]['content_score']
                    else:
                        content_score = 0
                #if parent_node is not None:
                    #pweight = self.class_weight(parent_node) + content_score
                    #pname = describe(parent_node)
                #else:
                    #pweight = 0
                    #pname = "no parent"
                to_remove = False
                reason = ""

                #if el.tag == 'div' and counts["img"] >= 1:
                #    continue
                if counts["p"] and counts["img"] > counts["p"]:
                    reason = "too many images (%s)" % counts["img"]
                    to_remove = True
                elif counts["li"] > counts["p"] and tag != "ul" and tag != "ol":
                    reason = "more <li>s than <p>s"
                    to_remove = True
                elif counts["input"] > (counts["p"] / 3):
                    reason = "less than 3x <p>s than <input>s"
                    to_remove = True
                elif content_length < (MIN_LEN) and (counts["img"] == 0 or counts["img"] > 2):
                    reason = "too short content length %s without a single image" % content_length
                    to_remove = True
                elif weight < 25 and link_density > 0.2:
                        reason = "too many links %.3f for its weight %s" % (
                            link_density, weight)
                        to_remove = True
                elif weight >= 25 and link_density > 0.5:
                    reason = "too many links %.3f for its weight %s" % (
                        link_density, weight)
                    to_remove = True
                elif (counts["embed"] == 1 and content_length < 75) or counts["embed"] > 1:
                    reason = "<embed>s with too short content length, or too many <embed>s"
                    to_remove = True
#                if el.tag == 'div' and counts['img'] >= 1 and to_remove:
#                    imgs = el.findall('.//img')
#                    valid_img = False
#                    self.debug(tounicode(el))
#                    for img in imgs:
#
#                        height = img.get('height')
#                        text_length = img.get('text_length')
#                        self.debug ("height %s text_length %s" %(repr(height), repr(text_length)))
#                        if to_int(height) >= 100 or to_int(text_length) >= 100:
#                            valid_img = True
#                            self.debug("valid image" + tounicode(img))
#                            break
#                    if valid_img:
#                        to_remove = False
#                        self.debug("Allowing %s" %el.text_content())
#                        for desnode in self.tags(el, "table", "ul", "div"):
#                            allowed[desnode] = True

                    #find x non empty preceding and succeeding siblings
                    i, j = 0, 0
                    x = 1
                    siblings = []
                    for sib in el.itersiblings():
                        #self.debug(sib.text_content())
                        sib_content_length = text_length(sib)
                        if sib_content_length:
                            i =+ 1
                            siblings.append(sib_content_length)
                            if i == x:
                                break
                    for sib in el.itersiblings(preceding=True):
                        #self.debug(sib.text_content())
                        sib_content_length = text_length(sib)
                        if sib_content_length:
                            j =+ 1
                            siblings.append(sib_content_length)
                            if j == x:
                                break
                    #self.debug(str(siblings))
                    if siblings and sum(siblings) > 1000:
                        to_remove = False
                        self.debug("Allowing %s" % describe(el))
                        for desnode in self.tags(el, "table", "ul", "div"):
                            allowed[desnode] = True

                if to_remove:
                    self.debug("Cleaned %6.3f %s with weight %s cause it has %s." %
                        (content_score, describe(el), weight, reason))
                    #print tounicode(el)
                    #self.debug("pname %s pweight %.3f" %(pname, pweight))
                    el.drop_tree()

        for el in ([node] + [n for n in node.iter()]):
            if not self.options.get('attributes', None):
                #el.attrib = {} #FIXME:Checkout the effects of disabling this
                pass

        return clean_attributes(tounicode(node))


class HashableElement():
    def __init__(self, node):
        self.node = node
        self._path = None

    def _get_path(self):
        if self._path is None:
            reverse_path = []
            node = self.node
            while node is not None:
                node_id = (node.tag, tuple(node.attrib.items()), node.text)
                reverse_path.append(node_id)
                node = node.getparent()
            self._path = tuple(reverse_path)
        return self._path
    path = property(_get_path)

    def __hash__(self):
        return hash(self.path)

    def __eq__(self, other):
        return self.path == other.path

    def __getattr__(self, tag):
        return getattr(self.node, tag)


def main():
    from optparse import OptionParser
    parser = OptionParser(usage="%prog: [options] [file]")
    parser.add_option('-v', '--verbose', action='store_true')
    parser.add_option('-u', '--url', default=None, help="use URL instead of a local file")
    (options, args) = parser.parse_args()

    if not (len(args) == 1 or options.url):
        parser.print_help()
        sys.exit(1)

    file = None
    if options.url:
        import urllib
        file = urllib.urlopen(options.url)
    else:
        file = open(args[0], 'rt')
    enc = sys.__stdout__.encoding or 'utf-8'
    try:
        print Document(file.read(),
            debug=options.verbose,
            url=options.url).summary().encode(enc, 'replace')
    finally:
        file.close()

if __name__ == '__main__':
    main()