Source code for w3lib.encoding

# -*- coding: utf-8 -*-
"""
Functions for handling encoding of web pages
"""
import re, codecs, encodings
from sys import version_info

_HEADER_ENCODING_RE = re.compile(r'charset=([\w-]+)', re.I)

[docs]def http_content_type_encoding(content_type): """Extract the encoding in the content-type header >>> import w3lib.encoding >>> w3lib.encoding.http_content_type_encoding("Content-Type: text/html; charset=ISO-8859-4") 'iso8859-4' """ if content_type: match = _HEADER_ENCODING_RE.search(content_type) if match: return resolve_encoding(match.group(1))
# regexp for parsing HTTP meta tags _TEMPLATE = r'''%s\s*=\s*["']?\s*%s\s*["']?''' _SKIP_ATTRS = '''(?:\\s+ [^=<>/\\s"'\x00-\x1f\x7f]+ # Attribute name (?:\\s*=\\s* (?: # ' and " are entity encoded (&apos;, &quot;), so no need for \', \" '[^']*' # attr in ' | "[^"]*" # attr in " | [^'"\\s]+ # attr having no ' nor " ))? )*?''' # must be used with re.VERBOSE flag _HTTPEQUIV_RE = _TEMPLATE % ('http-equiv', 'Content-Type') _CONTENT_RE = _TEMPLATE % ('content', r'(?P<mime>[^;]+);\s*charset=(?P<charset>[\w-]+)') _CONTENT2_RE = _TEMPLATE % ('charset', r'(?P<charset2>[\w-]+)') _XML_ENCODING_RE = _TEMPLATE % ('encoding', r'(?P<xmlcharset>[\w-]+)') # check for meta tags, or xml decl. and stop search if a body tag is encountered _BODY_ENCODING_PATTERN = r'<\s*(?:meta%s(?:(?:\s+%s|\s+%s){2}|\s+%s)|\?xml\s[^>]+%s|body)' % ( _SKIP_ATTRS, _HTTPEQUIV_RE, _CONTENT_RE, _CONTENT2_RE, _XML_ENCODING_RE) _BODY_ENCODING_STR_RE = re.compile(_BODY_ENCODING_PATTERN, re.I | re.VERBOSE) _BODY_ENCODING_BYTES_RE = re.compile(_BODY_ENCODING_PATTERN.encode('ascii'), re.I | re.VERBOSE)
[docs]def html_body_declared_encoding(html_body_str): '''Return the encoding specified in meta tags in the html body, or ``None`` if no suitable encoding was found >>> import w3lib.encoding >>> w3lib.encoding.html_body_declared_encoding( ... """<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" ... "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> ... <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> ... <head> ... <title>Some title</title> ... <meta http-equiv="content-type" content="text/html;charset=utf-8" /> ... </head> ... <body> ... ... ... </body> ... </html>""") 'utf-8' >>> ''' # html5 suggests the first 1024 bytes are sufficient, we allow for more chunk = html_body_str[:4096] if isinstance(chunk, bytes): match = _BODY_ENCODING_BYTES_RE.search(chunk) else: match = _BODY_ENCODING_STR_RE.search(chunk) if match: encoding = match.group('charset') or match.group('charset2') \ or match.group('xmlcharset') if encoding: return resolve_encoding(encoding)
# Default encoding translation # this maps cannonicalized encodings to target encodings # see http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#character-encodings-0 # in addition, gb18030 supercedes gb2312 & gbk # the keys are converted using _c18n_encoding and in sorted order DEFAULT_ENCODING_TRANSLATION = { 'ascii': 'cp1252', 'big5': 'big5hkscs', 'euc_kr': 'cp949', 'gb2312': 'gb18030', 'gb_2312_80': 'gb18030', 'gbk': 'gb18030', 'iso8859_11': 'cp874', 'iso8859_9': 'cp1254', 'latin_1': 'cp1252', 'macintosh': 'mac_roman', 'shift_jis': 'cp932', 'tis_620': 'cp874', 'win_1251': 'cp1251', 'windows_31j': 'cp932', 'win_31j': 'cp932', 'windows_874': 'cp874', 'win_874': 'cp874', 'x_sjis': 'cp932', 'zh_cn': 'gb18030' } def _c18n_encoding(encoding): """Canonicalize an encoding name This performs normalization and translates aliases using python's encoding aliases """ normed = encodings.normalize_encoding(encoding).lower() return encodings.aliases.aliases.get(normed, normed)
[docs]def resolve_encoding(encoding_alias): """Return the encoding that `encoding_alias` maps to, or ``None`` if the encoding cannot be interpreted >>> import w3lib.encoding >>> w3lib.encoding.resolve_encoding('latin1') 'cp1252' >>> w3lib.encoding.resolve_encoding('gb_2312-80') 'gb18030' >>> """ c18n_encoding = _c18n_encoding(encoding_alias) translated = DEFAULT_ENCODING_TRANSLATION.get(c18n_encoding, c18n_encoding) try: return codecs.lookup(translated).name except LookupError: return None
_BOM_TABLE = [ (codecs.BOM_UTF32_BE, 'utf-32-be'), (codecs.BOM_UTF32_LE, 'utf-32-le'), (codecs.BOM_UTF16_BE, 'utf-16-be'), (codecs.BOM_UTF16_LE, 'utf-16-le'), (codecs.BOM_UTF8, 'utf-8') ] _FIRST_CHARS = set(c[0] for (c, _) in _BOM_TABLE)
[docs]def read_bom(data): r"""Read the byte order mark in the text, if present, and return the encoding represented by the BOM and the BOM. If no BOM can be detected, ``(None, None)`` is returned. >>> import w3lib.encoding >>> w3lib.encoding.read_bom(b'\xfe\xff\x6c\x34') ('utf-16-be', '\xfe\xff') >>> w3lib.encoding.read_bom(b'\xff\xfe\x34\x6c') ('utf-16-le', '\xff\xfe') >>> w3lib.encoding.read_bom(b'\x00\x00\xfe\xff\x00\x00\x6c\x34') ('utf-32-be', '\x00\x00\xfe\xff') >>> w3lib.encoding.read_bom(b'\xff\xfe\x00\x00\x34\x6c\x00\x00') ('utf-32-le', '\xff\xfe\x00\x00') >>> w3lib.encoding.read_bom(b'\x01\x02\x03\x04') (None, None) >>> """ # common case is no BOM, so this is fast if data and data[0] in _FIRST_CHARS: for bom, encoding in _BOM_TABLE: if data.startswith(bom): return encoding, bom return None, None
# Python decoder doesn't follow unicode standard when handling # bad utf-8 encoded strings. see http://bugs.python.org/issue8271 codecs.register_error('w3lib_replace', lambda exc: (u'\ufffd', exc.end))
[docs]def to_unicode(data_str, encoding): """Convert a str object to unicode using the encoding given Characters that cannot be converted will be converted to ``\\ufffd`` (the unicode replacement character). """ return data_str.decode(encoding, 'replace' if version_info[0:2] >= (3, 3) else 'w3lib_replace')
[docs]def html_to_unicode(content_type_header, html_body_str, default_encoding='utf8', auto_detect_fun=None): r'''Convert raw html bytes to unicode This attempts to make a reasonable guess at the content encoding of the html body, following a similar process to a web browser. It will try in order: * http content type header * BOM (byte-order mark) * meta or xml tag declarations * auto-detection, if the `auto_detect_fun` keyword argument is not ``None`` * default encoding in keyword arg (which defaults to utf8) If an encoding other than the auto-detected or default encoding is used, overrides will be applied, converting some character encodings to more suitable alternatives. If a BOM is found matching the encoding, it will be stripped. The `auto_detect_fun` argument can be used to pass a function that will sniff the encoding of the text. This function must take the raw text as an argument and return the name of an encoding that python can process, or None. To use chardet, for example, you can define the function as:: auto_detect_fun=lambda x: chardet.detect(x).get('encoding') or to use UnicodeDammit (shipped with the BeautifulSoup library):: auto_detect_fun=lambda x: UnicodeDammit(x).originalEncoding If the locale of the website or user language preference is known, then a better default encoding can be supplied. If `content_type_header` is not present, ``None`` can be passed signifying that the header was not present. This method will not fail, if characters cannot be converted to unicode, ``\\ufffd`` (the unicode replacement character) will be inserted instead. Returns a tuple of ``(<encoding used>, <unicode_string>)`` Examples: >>> import w3lib.encoding >>> w3lib.encoding.html_to_unicode(None, ... b"""<!DOCTYPE html> ... <head> ... <meta charset="UTF-8" /> ... <meta name="viewport" content="width=device-width" /> ... <title>Creative Commons France</title> ... <link rel='canonical' href='http://creativecommons.fr/' /> ... <body> ... <p>Creative Commons est une organisation \xc3\xa0 but non lucratif ... qui a pour dessein de faciliter la diffusion et le partage des oeuvres ... tout en accompagnant les nouvelles pratiques de cr\xc3\xa9ation \xc3\xa0 l\xe2\x80\x99\xc3\xa8re numerique.</p> ... </body> ... </html>""") ('utf-8', u'<!DOCTYPE html>\n<head>\n<meta charset="UTF-8" />\n<meta name="viewport" content="width=device-width" />\n<title>Creative Commons France</title>\n<link rel=\'canonical\' href=\'http://creativecommons.fr/\' />\n<body>\n<p>Creative Commons est une organisation \xe0 but non lucratif\nqui a pour dessein de faciliter la diffusion et le partage des oeuvres\ntout en accompagnant les nouvelles pratiques de cr\xe9ation \xe0 l\u2019\xe8re numerique.</p>\n</body>\n</html>') >>> ''' enc = http_content_type_encoding(content_type_header) bom_enc, bom = read_bom(html_body_str) if enc is not None: # remove BOM if it agrees with the encoding if enc == bom_enc: html_body_str = html_body_str[len(bom):] elif enc == 'utf-16' or enc == 'utf-32': # read endianness from BOM, or default to big endian # tools.ietf.org/html/rfc2781 section 4.3 if bom_enc is not None and bom_enc.startswith(enc): enc = bom_enc html_body_str = html_body_str[len(bom):] else: enc += '-be' return enc, to_unicode(html_body_str, enc) if bom_enc is not None: return bom_enc, to_unicode(html_body_str[len(bom):], bom_enc) enc = html_body_declared_encoding(html_body_str) if enc is None and (auto_detect_fun is not None): enc = auto_detect_fun(html_body_str) if enc is None: enc = default_encoding return enc, to_unicode(html_body_str, enc)