500 lines
19 KiB
Python
500 lines
19 KiB
Python
# encoding: utf-8
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"""Use the HTMLParser library to parse HTML files that aren't too bad."""
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# Use of this source code is governed by the MIT license.
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__license__ = "MIT"
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__all__ = [
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'HTMLParserTreeBuilder',
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]
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from html.parser import HTMLParser
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try:
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from html.parser import HTMLParseError
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except ImportError as e:
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# HTMLParseError is removed in Python 3.5. Since it can never be
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# thrown in 3.5, we can just define our own class as a placeholder.
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class HTMLParseError(Exception):
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pass
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import sys
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import warnings
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# Starting in Python 3.2, the HTMLParser constructor takes a 'strict'
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# argument, which we'd like to set to False. Unfortunately,
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# http://bugs.python.org/issue13273 makes strict=True a better bet
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# before Python 3.2.3.
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#
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# At the end of this file, we monkeypatch HTMLParser so that
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# strict=True works well on Python 3.2.2.
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major, minor, release = sys.version_info[:3]
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CONSTRUCTOR_TAKES_STRICT = major == 3 and minor == 2 and release >= 3
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CONSTRUCTOR_STRICT_IS_DEPRECATED = major == 3 and minor == 3
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CONSTRUCTOR_TAKES_CONVERT_CHARREFS = major == 3 and minor >= 4
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from bs4.element import (
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CData,
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Comment,
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Declaration,
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Doctype,
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ProcessingInstruction,
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)
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from bs4.dammit import EntitySubstitution, UnicodeDammit
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from bs4.builder import (
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DetectsXMLParsedAsHTML,
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HTML,
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HTMLTreeBuilder,
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STRICT,
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)
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HTMLPARSER = 'html.parser'
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class BeautifulSoupHTMLParser(HTMLParser, DetectsXMLParsedAsHTML):
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"""A subclass of the Python standard library's HTMLParser class, which
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listens for HTMLParser events and translates them into calls
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to Beautiful Soup's tree construction API.
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"""
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# Strategies for handling duplicate attributes
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IGNORE = 'ignore'
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REPLACE = 'replace'
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def __init__(self, *args, **kwargs):
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"""Constructor.
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:param on_duplicate_attribute: A strategy for what to do if a
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tag includes the same attribute more than once. Accepted
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values are: REPLACE (replace earlier values with later
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ones, the default), IGNORE (keep the earliest value
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encountered), or a callable. A callable must take three
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arguments: the dictionary of attributes already processed,
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the name of the duplicate attribute, and the most recent value
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encountered.
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"""
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self.on_duplicate_attribute = kwargs.pop(
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'on_duplicate_attribute', self.REPLACE
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)
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HTMLParser.__init__(self, *args, **kwargs)
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# Keep a list of empty-element tags that were encountered
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# without an explicit closing tag. If we encounter a closing tag
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# of this type, we'll associate it with one of those entries.
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#
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# This isn't a stack because we don't care about the
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# order. It's a list of closing tags we've already handled and
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# will ignore, assuming they ever show up.
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self.already_closed_empty_element = []
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self._initialize_xml_detector()
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def error(self, msg):
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"""In Python 3, HTMLParser subclasses must implement error(), although
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this requirement doesn't appear to be documented.
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In Python 2, HTMLParser implements error() by raising an exception,
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which we don't want to do.
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In any event, this method is called only on very strange
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markup and our best strategy is to pretend it didn't happen
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and keep going.
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"""
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warnings.warn(msg)
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def handle_startendtag(self, name, attrs):
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"""Handle an incoming empty-element tag.
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This is only called when the markup looks like <tag/>.
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:param name: Name of the tag.
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:param attrs: Dictionary of the tag's attributes.
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"""
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# is_startend() tells handle_starttag not to close the tag
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# just because its name matches a known empty-element tag. We
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# know that this is an empty-element tag and we want to call
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# handle_endtag ourselves.
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tag = self.handle_starttag(name, attrs, handle_empty_element=False)
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self.handle_endtag(name)
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def handle_starttag(self, name, attrs, handle_empty_element=True):
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"""Handle an opening tag, e.g. '<tag>'
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:param name: Name of the tag.
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:param attrs: Dictionary of the tag's attributes.
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:param handle_empty_element: True if this tag is known to be
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an empty-element tag (i.e. there is not expected to be any
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closing tag).
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"""
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# XXX namespace
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attr_dict = {}
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for key, value in attrs:
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# Change None attribute values to the empty string
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# for consistency with the other tree builders.
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if value is None:
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value = ''
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if key in attr_dict:
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# A single attribute shows up multiple times in this
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# tag. How to handle it depends on the
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# on_duplicate_attribute setting.
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on_dupe = self.on_duplicate_attribute
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if on_dupe == self.IGNORE:
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pass
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elif on_dupe in (None, self.REPLACE):
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attr_dict[key] = value
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else:
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on_dupe(attr_dict, key, value)
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else:
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attr_dict[key] = value
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attrvalue = '""'
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#print("START", name)
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sourceline, sourcepos = self.getpos()
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tag = self.soup.handle_starttag(
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name, None, None, attr_dict, sourceline=sourceline,
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sourcepos=sourcepos
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)
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if tag and tag.is_empty_element and handle_empty_element:
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# Unlike other parsers, html.parser doesn't send separate end tag
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# events for empty-element tags. (It's handled in
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# handle_startendtag, but only if the original markup looked like
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# <tag/>.)
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#
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# So we need to call handle_endtag() ourselves. Since we
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# know the start event is identical to the end event, we
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# don't want handle_endtag() to cross off any previous end
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# events for tags of this name.
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self.handle_endtag(name, check_already_closed=False)
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# But we might encounter an explicit closing tag for this tag
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# later on. If so, we want to ignore it.
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self.already_closed_empty_element.append(name)
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if self._root_tag is None:
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self._root_tag_encountered(name)
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def handle_endtag(self, name, check_already_closed=True):
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"""Handle a closing tag, e.g. '</tag>'
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:param name: A tag name.
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:param check_already_closed: True if this tag is expected to
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be the closing portion of an empty-element tag,
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e.g. '<tag></tag>'.
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"""
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#print("END", name)
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if check_already_closed and name in self.already_closed_empty_element:
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# This is a redundant end tag for an empty-element tag.
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# We've already called handle_endtag() for it, so just
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# check it off the list.
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#print("ALREADY CLOSED", name)
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self.already_closed_empty_element.remove(name)
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else:
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self.soup.handle_endtag(name)
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def handle_data(self, data):
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"""Handle some textual data that shows up between tags."""
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self.soup.handle_data(data)
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def handle_charref(self, name):
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"""Handle a numeric character reference by converting it to the
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corresponding Unicode character and treating it as textual
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data.
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:param name: Character number, possibly in hexadecimal.
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"""
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# XXX workaround for a bug in HTMLParser. Remove this once
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# it's fixed in all supported versions.
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# http://bugs.python.org/issue13633
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if name.startswith('x'):
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real_name = int(name.lstrip('x'), 16)
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elif name.startswith('X'):
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real_name = int(name.lstrip('X'), 16)
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else:
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real_name = int(name)
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data = None
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if real_name < 256:
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# HTML numeric entities are supposed to reference Unicode
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# code points, but sometimes they reference code points in
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# some other encoding (ahem, Windows-1252). E.g. “
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# instead of É for LEFT DOUBLE QUOTATION MARK. This
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# code tries to detect this situation and compensate.
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for encoding in (self.soup.original_encoding, 'windows-1252'):
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if not encoding:
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continue
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try:
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data = bytearray([real_name]).decode(encoding)
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except UnicodeDecodeError as e:
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pass
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if not data:
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try:
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data = chr(real_name)
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except (ValueError, OverflowError) as e:
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pass
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data = data or "\N{REPLACEMENT CHARACTER}"
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self.handle_data(data)
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def handle_entityref(self, name):
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"""Handle a named entity reference by converting it to the
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corresponding Unicode character(s) and treating it as textual
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data.
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:param name: Name of the entity reference.
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"""
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character = EntitySubstitution.HTML_ENTITY_TO_CHARACTER.get(name)
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if character is not None:
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data = character
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else:
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# If this were XML, it would be ambiguous whether "&foo"
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# was an character entity reference with a missing
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# semicolon or the literal string "&foo". Since this is
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# HTML, we have a complete list of all character entity references,
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# and this one wasn't found, so assume it's the literal string "&foo".
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data = "&%s" % name
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self.handle_data(data)
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def handle_comment(self, data):
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"""Handle an HTML comment.
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:param data: The text of the comment.
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"""
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self.soup.endData()
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self.soup.handle_data(data)
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self.soup.endData(Comment)
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def handle_decl(self, data):
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"""Handle a DOCTYPE declaration.
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:param data: The text of the declaration.
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"""
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self.soup.endData()
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data = data[len("DOCTYPE "):]
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self.soup.handle_data(data)
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self.soup.endData(Doctype)
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def unknown_decl(self, data):
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"""Handle a declaration of unknown type -- probably a CDATA block.
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:param data: The text of the declaration.
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"""
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if data.upper().startswith('CDATA['):
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cls = CData
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data = data[len('CDATA['):]
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else:
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cls = Declaration
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self.soup.endData()
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self.soup.handle_data(data)
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self.soup.endData(cls)
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def handle_pi(self, data):
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"""Handle a processing instruction.
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:param data: The text of the instruction.
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"""
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self.soup.endData()
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self.soup.handle_data(data)
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self._document_might_be_xml(data)
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self.soup.endData(ProcessingInstruction)
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class HTMLParserTreeBuilder(HTMLTreeBuilder):
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"""A Beautiful soup `TreeBuilder` that uses the `HTMLParser` parser,
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found in the Python standard library.
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"""
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is_xml = False
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picklable = True
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NAME = HTMLPARSER
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features = [NAME, HTML, STRICT]
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# The html.parser knows which line number and position in the
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# original file is the source of an element.
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TRACKS_LINE_NUMBERS = True
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def __init__(self, parser_args=None, parser_kwargs=None, **kwargs):
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"""Constructor.
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:param parser_args: Positional arguments to pass into
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the BeautifulSoupHTMLParser constructor, once it's
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invoked.
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:param parser_kwargs: Keyword arguments to pass into
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the BeautifulSoupHTMLParser constructor, once it's
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invoked.
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:param kwargs: Keyword arguments for the superclass constructor.
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"""
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# Some keyword arguments will be pulled out of kwargs and placed
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# into parser_kwargs.
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extra_parser_kwargs = dict()
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for arg in ('on_duplicate_attribute',):
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if arg in kwargs:
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value = kwargs.pop(arg)
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extra_parser_kwargs[arg] = value
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super(HTMLParserTreeBuilder, self).__init__(**kwargs)
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parser_args = parser_args or []
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parser_kwargs = parser_kwargs or {}
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parser_kwargs.update(extra_parser_kwargs)
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if CONSTRUCTOR_TAKES_STRICT and not CONSTRUCTOR_STRICT_IS_DEPRECATED:
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parser_kwargs['strict'] = False
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if CONSTRUCTOR_TAKES_CONVERT_CHARREFS:
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parser_kwargs['convert_charrefs'] = False
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self.parser_args = (parser_args, parser_kwargs)
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def prepare_markup(self, markup, user_specified_encoding=None,
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document_declared_encoding=None, exclude_encodings=None):
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"""Run any preliminary steps necessary to make incoming markup
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acceptable to the parser.
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:param markup: Some markup -- probably a bytestring.
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:param user_specified_encoding: The user asked to try this encoding.
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:param document_declared_encoding: The markup itself claims to be
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in this encoding.
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:param exclude_encodings: The user asked _not_ to try any of
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these encodings.
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:yield: A series of 4-tuples:
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(markup, encoding, declared encoding,
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has undergone character replacement)
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Each 4-tuple represents a strategy for converting the
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document to Unicode and parsing it. Each strategy will be tried
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in turn.
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"""
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if isinstance(markup, str):
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# Parse Unicode as-is.
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yield (markup, None, None, False)
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return
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# Ask UnicodeDammit to sniff the most likely encoding.
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# This was provided by the end-user; treat it as a known
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# definite encoding per the algorithm laid out in the HTML5
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# spec. (See the EncodingDetector class for details.)
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known_definite_encodings = [user_specified_encoding]
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# This was found in the document; treat it as a slightly lower-priority
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# user encoding.
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user_encodings = [document_declared_encoding]
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try_encodings = [user_specified_encoding, document_declared_encoding]
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dammit = UnicodeDammit(
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markup,
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known_definite_encodings=known_definite_encodings,
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user_encodings=user_encodings,
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is_html=True,
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exclude_encodings=exclude_encodings
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)
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yield (dammit.markup, dammit.original_encoding,
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dammit.declared_html_encoding,
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dammit.contains_replacement_characters)
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def feed(self, markup):
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"""Run some incoming markup through some parsing process,
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populating the `BeautifulSoup` object in self.soup.
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"""
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args, kwargs = self.parser_args
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parser = BeautifulSoupHTMLParser(*args, **kwargs)
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parser.soup = self.soup
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try:
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parser.feed(markup)
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parser.close()
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except HTMLParseError as e:
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warnings.warn(RuntimeWarning(
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"Python's built-in HTMLParser cannot parse the given document. This is not a bug in Beautiful Soup. The best solution is to install an external parser (lxml or html5lib), and use Beautiful Soup with that parser. See http://www.crummy.com/software/BeautifulSoup/bs4/doc/#installing-a-parser for help."))
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raise e
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parser.already_closed_empty_element = []
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# Patch 3.2 versions of HTMLParser earlier than 3.2.3 to use some
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# 3.2.3 code. This ensures they don't treat markup like <p></p> as a
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# string.
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#
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# XXX This code can be removed once most Python 3 users are on 3.2.3.
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if major == 3 and minor == 2 and not CONSTRUCTOR_TAKES_STRICT:
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import re
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attrfind_tolerant = re.compile(
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r'\s*((?<=[\'"\s])[^\s/>][^\s/=>]*)(\s*=+\s*'
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r'(\'[^\']*\'|"[^"]*"|(?![\'"])[^>\s]*))?')
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HTMLParserTreeBuilder.attrfind_tolerant = attrfind_tolerant
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locatestarttagend = re.compile(r"""
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<[a-zA-Z][-.a-zA-Z0-9:_]* # tag name
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(?:\s+ # whitespace before attribute name
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(?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name
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(?:\s*=\s* # value indicator
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(?:'[^']*' # LITA-enclosed value
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|\"[^\"]*\" # LIT-enclosed value
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|[^'\">\s]+ # bare value
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)
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)?
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)
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)*
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\s* # trailing whitespace
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""", re.VERBOSE)
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BeautifulSoupHTMLParser.locatestarttagend = locatestarttagend
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from html.parser import tagfind, attrfind
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def parse_starttag(self, i):
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self.__starttag_text = None
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endpos = self.check_for_whole_start_tag(i)
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if endpos < 0:
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return endpos
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rawdata = self.rawdata
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self.__starttag_text = rawdata[i:endpos]
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# Now parse the data between i+1 and j into a tag and attrs
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attrs = []
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match = tagfind.match(rawdata, i+1)
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assert match, 'unexpected call to parse_starttag()'
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k = match.end()
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self.lasttag = tag = rawdata[i+1:k].lower()
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while k < endpos:
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if self.strict:
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m = attrfind.match(rawdata, k)
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else:
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m = attrfind_tolerant.match(rawdata, k)
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if not m:
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break
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attrname, rest, attrvalue = m.group(1, 2, 3)
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if not rest:
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attrvalue = None
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elif attrvalue[:1] == '\'' == attrvalue[-1:] or \
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attrvalue[:1] == '"' == attrvalue[-1:]:
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attrvalue = attrvalue[1:-1]
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if attrvalue:
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attrvalue = self.unescape(attrvalue)
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attrs.append((attrname.lower(), attrvalue))
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k = m.end()
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end = rawdata[k:endpos].strip()
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if end not in (">", "/>"):
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lineno, offset = self.getpos()
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if "\n" in self.__starttag_text:
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lineno = lineno + self.__starttag_text.count("\n")
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offset = len(self.__starttag_text) \
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- self.__starttag_text.rfind("\n")
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else:
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offset = offset + len(self.__starttag_text)
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if self.strict:
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self.error("junk characters in start tag: %r"
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% (rawdata[k:endpos][:20],))
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self.handle_data(rawdata[i:endpos])
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return endpos
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if end.endswith('/>'):
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# XHTML-style empty tag: <span attr="value" />
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self.handle_startendtag(tag, attrs)
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else:
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self.handle_starttag(tag, attrs)
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if tag in self.CDATA_CONTENT_ELEMENTS:
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self.set_cdata_mode(tag)
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return endpos
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def set_cdata_mode(self, elem):
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self.cdata_elem = elem.lower()
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self.interesting = re.compile(r'</\s*%s\s*>' % self.cdata_elem, re.I)
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BeautifulSoupHTMLParser.parse_starttag = parse_starttag
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BeautifulSoupHTMLParser.set_cdata_mode = set_cdata_mode
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CONSTRUCTOR_TAKES_STRICT = True
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