blob: 765f1c8334e5cbe1fa877e29bd21c1562d47fc1d [file] [log] [blame]
"""Parse (absolute and relative) URLs.
urlparse module is based upon the following RFC specifications.
RFC 3986 (STD66): "Uniform Resource Identifiers" by T. Berners-Lee, R. Fielding
and L. Masinter, January 2005.
RFC 2396: "Uniform Resource Identifiers (URI)": Generic Syntax by T.
Berners-Lee, R. Fielding, and L. Masinter, August 1998.
RFC 2368: "The mailto URL scheme", by P.Hoffman , L Masinter, J. Zwinski, July 1998.
RFC 1808: "Relative Uniform Resource Locators", by R. Fielding, UC Irvine, June
1995.
RFC 1738: "Uniform Resource Locators (URL)" by T. Berners-Lee, L. Masinter, M.
McCahill, December 1994
RFC 3986 is considered the current standard and any future changes to
urlparse module should conform with it. The urlparse module is
currently not entirely compliant with this RFC due to defacto
scenarios for parsing, and for backward compatibility purposes, some
parsing quirks from older RFCs are retained. The testcases in
test_urlparse.py provides a good indicator of parsing behavior.
"""
import sys
import collections
__all__ = ["urlparse", "urlunparse", "urljoin", "urldefrag",
"urlsplit", "urlunsplit", "parse_qs", "parse_qsl",
"quote", "quote_plus", "quote_from_bytes",
"unquote", "unquote_plus", "unquote_to_bytes"]
# A classification of schemes ('' means apply by default)
uses_relative = ['ftp', 'http', 'gopher', 'nntp', 'imap',
'wais', 'file', 'https', 'shttp', 'mms',
'prospero', 'rtsp', 'rtspu', '', 'sftp']
uses_netloc = ['ftp', 'http', 'gopher', 'nntp', 'telnet',
'imap', 'wais', 'file', 'mms', 'https', 'shttp',
'snews', 'prospero', 'rtsp', 'rtspu', 'rsync', '',
'svn', 'svn+ssh', 'sftp', 'nfs', 'git', 'git+ssh']
non_hierarchical = ['gopher', 'hdl', 'mailto', 'news',
'telnet', 'wais', 'imap', 'snews', 'sip', 'sips']
uses_params = ['ftp', 'hdl', 'prospero', 'http', 'imap',
'https', 'shttp', 'rtsp', 'rtspu', 'sip', 'sips',
'mms', '', 'sftp']
uses_query = ['http', 'wais', 'imap', 'https', 'shttp', 'mms',
'gopher', 'rtsp', 'rtspu', 'sip', 'sips', '']
uses_fragment = ['ftp', 'hdl', 'http', 'gopher', 'news',
'nntp', 'wais', 'https', 'shttp', 'snews',
'file', 'prospero', '']
# Characters valid in scheme names
scheme_chars = ('abcdefghijklmnopqrstuvwxyz'
'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
'0123456789'
'+-.')
MAX_CACHE_SIZE = 20
_parse_cache = {}
def clear_cache():
"""Clear the parse cache and the quoters cache."""
_parse_cache.clear()
_safe_quoters.clear()
class ResultMixin(object):
"""Shared methods for the parsed result objects."""
@property
def username(self):
netloc = self.netloc
if "@" in netloc:
userinfo = netloc.rsplit("@", 1)[0]
if ":" in userinfo:
userinfo = userinfo.split(":", 1)[0]
return userinfo
return None
@property
def password(self):
netloc = self.netloc
if "@" in netloc:
userinfo = netloc.rsplit("@", 1)[0]
if ":" in userinfo:
return userinfo.split(":", 1)[1]
return None
@property
def hostname(self):
netloc = self.netloc
if "@" in netloc:
netloc = netloc.rsplit("@", 1)[1]
if ":" in netloc:
netloc = netloc.split(":", 1)[0]
return netloc.lower() or None
@property
def port(self):
netloc = self.netloc
if "@" in netloc:
netloc = netloc.rsplit("@", 1)[1]
if ":" in netloc:
port = netloc.split(":", 1)[1]
return int(port, 10)
return None
from collections import namedtuple
class SplitResult(namedtuple('SplitResult', 'scheme netloc path query fragment'), ResultMixin):
__slots__ = ()
def geturl(self):
return urlunsplit(self)
class ParseResult(namedtuple('ParseResult', 'scheme netloc path params query fragment'), ResultMixin):
__slots__ = ()
def geturl(self):
return urlunparse(self)
def urlparse(url, scheme='', allow_fragments=True):
"""Parse a URL into 6 components:
<scheme>://<netloc>/<path>;<params>?<query>#<fragment>
Return a 6-tuple: (scheme, netloc, path, params, query, fragment).
Note that we don't break the components up in smaller bits
(e.g. netloc is a single string) and we don't expand % escapes."""
tuple = urlsplit(url, scheme, allow_fragments)
scheme, netloc, url, query, fragment = tuple
if scheme in uses_params and ';' in url:
url, params = _splitparams(url)
else:
params = ''
return ParseResult(scheme, netloc, url, params, query, fragment)
def _splitparams(url):
if '/' in url:
i = url.find(';', url.rfind('/'))
if i < 0:
return url, ''
else:
i = url.find(';')
return url[:i], url[i+1:]
def _splitnetloc(url, start=0):
delim = len(url) # position of end of domain part of url, default is end
for c in '/?#': # look for delimiters; the order is NOT important
wdelim = url.find(c, start) # find first of this delim
if wdelim >= 0: # if found
delim = min(delim, wdelim) # use earliest delim position
return url[start:delim], url[delim:] # return (domain, rest)
def urlsplit(url, scheme='', allow_fragments=True):
"""Parse a URL into 5 components:
<scheme>://<netloc>/<path>?<query>#<fragment>
Return a 5-tuple: (scheme, netloc, path, query, fragment).
Note that we don't break the components up in smaller bits
(e.g. netloc is a single string) and we don't expand % escapes."""
allow_fragments = bool(allow_fragments)
key = url, scheme, allow_fragments, type(url), type(scheme)
cached = _parse_cache.get(key, None)
if cached:
return cached
if len(_parse_cache) >= MAX_CACHE_SIZE: # avoid runaway growth
clear_cache()
netloc = query = fragment = ''
i = url.find(':')
if i > 0:
if url[:i] == 'http': # optimize the common case
scheme = url[:i].lower()
url = url[i+1:]
if url[:2] == '//':
netloc, url = _splitnetloc(url, 2)
if allow_fragments and '#' in url:
url, fragment = url.split('#', 1)
if '?' in url:
url, query = url.split('?', 1)
v = SplitResult(scheme, netloc, url, query, fragment)
_parse_cache[key] = v
return v
if url.endswith(':') or not url[i+1].isdigit():
for c in url[:i]:
if c not in scheme_chars:
break
else:
scheme, url = url[:i].lower(), url[i+1:]
if url[:2] == '//':
netloc, url = _splitnetloc(url, 2)
if allow_fragments and scheme in uses_fragment and '#' in url:
url, fragment = url.split('#', 1)
if scheme in uses_query and '?' in url:
url, query = url.split('?', 1)
v = SplitResult(scheme, netloc, url, query, fragment)
_parse_cache[key] = v
return v
def urlunparse(components):
"""Put a parsed URL back together again. This may result in a
slightly different, but equivalent URL, if the URL that was parsed
originally had redundant delimiters, e.g. a ? with an empty query
(the draft states that these are equivalent)."""
scheme, netloc, url, params, query, fragment = components
if params:
url = "%s;%s" % (url, params)
return urlunsplit((scheme, netloc, url, query, fragment))
def urlunsplit(components):
"""Combine the elements of a tuple as returned by urlsplit() into a
complete URL as a string. The data argument can be any five-item iterable.
This may result in a slightly different, but equivalent URL, if the URL that
was parsed originally had unnecessary delimiters (for example, a ? with an
empty query; the RFC states that these are equivalent)."""
scheme, netloc, url, query, fragment = components
if netloc or (scheme and scheme in uses_netloc and url[:2] != '//'):
if url and url[:1] != '/': url = '/' + url
url = '//' + (netloc or '') + url
if scheme:
url = scheme + ':' + url
if query:
url = url + '?' + query
if fragment:
url = url + '#' + fragment
return url
def urljoin(base, url, allow_fragments=True):
"""Join a base URL and a possibly relative URL to form an absolute
interpretation of the latter."""
if not base:
return url
if not url:
return base
bscheme, bnetloc, bpath, bparams, bquery, bfragment = \
urlparse(base, '', allow_fragments)
scheme, netloc, path, params, query, fragment = \
urlparse(url, bscheme, allow_fragments)
if scheme != bscheme or scheme not in uses_relative:
return url
if scheme in uses_netloc:
if netloc:
return urlunparse((scheme, netloc, path,
params, query, fragment))
netloc = bnetloc
if path[:1] == '/':
return urlunparse((scheme, netloc, path,
params, query, fragment))
if not path:
path = bpath
if not params:
params = bparams
else:
path = path[:-1]
return urlunparse((scheme, netloc, path,
params, query, fragment))
if not query:
query = bquery
return urlunparse((scheme, netloc, path,
params, query, fragment))
segments = bpath.split('/')[:-1] + path.split('/')
# XXX The stuff below is bogus in various ways...
if segments[-1] == '.':
segments[-1] = ''
while '.' in segments:
segments.remove('.')
while 1:
i = 1
n = len(segments) - 1
while i < n:
if (segments[i] == '..'
and segments[i-1] not in ('', '..')):
del segments[i-1:i+1]
break
i = i+1
else:
break
if segments == ['', '..']:
segments[-1] = ''
elif len(segments) >= 2 and segments[-1] == '..':
segments[-2:] = ['']
return urlunparse((scheme, netloc, '/'.join(segments),
params, query, fragment))
def urldefrag(url):
"""Removes any existing fragment from URL.
Returns a tuple of the defragmented URL and the fragment. If
the URL contained no fragments, the second element is the
empty string.
"""
if '#' in url:
s, n, p, a, q, frag = urlparse(url)
defrag = urlunparse((s, n, p, a, q, ''))
return defrag, frag
else:
return url, ''
def unquote_to_bytes(string):
"""unquote_to_bytes('abc%20def') -> b'abc def'."""
# Note: strings are encoded as UTF-8. This is only an issue if it contains
# unescaped non-ASCII characters, which URIs should not.
if not string:
# Is it a string-like object?
string.split
return b''
if isinstance(string, str):
string = string.encode('utf-8')
res = string.split(b'%')
if len(res) == 1:
return string
string = res[0]
for item in res[1:]:
try:
string += bytes([int(item[:2], 16)]) + item[2:]
except ValueError:
string += b'%' + item
return string
def unquote(string, encoding='utf-8', errors='replace'):
"""Replace %xx escapes by their single-character equivalent. The optional
encoding and errors parameters specify how to decode percent-encoded
sequences into Unicode characters, as accepted by the bytes.decode()
method.
By default, percent-encoded sequences are decoded with UTF-8, and invalid
sequences are replaced by a placeholder character.
unquote('abc%20def') -> 'abc def'.
"""
if string == '':
return string
res = string.split('%')
if len(res) == 1:
return string
if encoding is None:
encoding = 'utf-8'
if errors is None:
errors = 'replace'
# pct_sequence: contiguous sequence of percent-encoded bytes, decoded
pct_sequence = b''
string = res[0]
for item in res[1:]:
try:
if not item:
raise ValueError
pct_sequence += bytes.fromhex(item[:2])
rest = item[2:]
if not rest:
# This segment was just a single percent-encoded character.
# May be part of a sequence of code units, so delay decoding.
# (Stored in pct_sequence).
continue
except ValueError:
rest = '%' + item
# Encountered non-percent-encoded characters. Flush the current
# pct_sequence.
string += pct_sequence.decode(encoding, errors) + rest
pct_sequence = b''
if pct_sequence:
# Flush the final pct_sequence
string += pct_sequence.decode(encoding, errors)
return string
def parse_qs(qs, keep_blank_values=False, strict_parsing=False):
"""Parse a query given as a string argument.
Arguments:
qs: percent-encoded query string to be parsed
keep_blank_values: flag indicating whether blank values in
percent-encoded queries should be treated as blank strings.
A true value indicates that blanks should be retained as
blank strings. The default false value indicates that
blank values are to be ignored and treated as if they were
not included.
strict_parsing: flag indicating what to do with parsing errors.
If false (the default), errors are silently ignored.
If true, errors raise a ValueError exception.
"""
dict = {}
for name, value in parse_qsl(qs, keep_blank_values, strict_parsing):
if name in dict:
dict[name].append(value)
else:
dict[name] = [value]
return dict
def parse_qsl(qs, keep_blank_values=False, strict_parsing=False):
"""Parse a query given as a string argument.
Arguments:
qs: percent-encoded query string to be parsed
keep_blank_values: flag indicating whether blank values in
percent-encoded queries should be treated as blank strings. A
true value indicates that blanks should be retained as blank
strings. The default false value indicates that blank values
are to be ignored and treated as if they were not included.
strict_parsing: flag indicating what to do with parsing errors. If
false (the default), errors are silently ignored. If true,
errors raise a ValueError exception.
Returns a list, as G-d intended.
"""
pairs = [s2 for s1 in qs.split('&') for s2 in s1.split(';')]
r = []
for name_value in pairs:
if not name_value and not strict_parsing:
continue
nv = name_value.split('=', 1)
if len(nv) != 2:
if strict_parsing:
raise ValueError("bad query field: %r" % (name_value,))
# Handle case of a control-name with no equal sign
if keep_blank_values:
nv.append('')
else:
continue
if len(nv[1]) or keep_blank_values:
name = unquote(nv[0].replace('+', ' '))
value = unquote(nv[1].replace('+', ' '))
r.append((name, value))
return r
def unquote_plus(string, encoding='utf-8', errors='replace'):
"""Like unquote(), but also replace plus signs by spaces, as required for
unquoting HTML form values.
unquote_plus('%7e/abc+def') -> '~/abc def'
"""
string = string.replace('+', ' ')
return unquote(string, encoding, errors)
_ALWAYS_SAFE = frozenset(b'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
b'abcdefghijklmnopqrstuvwxyz'
b'0123456789'
b'_.-')
_ALWAYS_SAFE_BYTES = bytes(_ALWAYS_SAFE)
_safe_quoters = {}
class Quoter(collections.defaultdict):
"""A mapping from bytes (in range(0,256)) to strings.
String values are percent-encoded byte values, unless the key < 128, and
in the "safe" set (either the specified safe set, or default set).
"""
# Keeps a cache internally, using defaultdict, for efficiency (lookups
# of cached keys don't call Python code at all).
def __init__(self, safe):
"""safe: bytes object."""
self.safe = _ALWAYS_SAFE.union(safe)
def __repr__(self):
# Without this, will just display as a defaultdict
return "<Quoter %r>" % dict(self)
def __missing__(self, b):
# Handle a cache miss. Store quoted string in cache and return.
res = chr(b) if b in self.safe else '%{:02X}'.format(b)
self[b] = res
return res
def quote(string, safe='/', encoding=None, errors=None):
"""quote('abc def') -> 'abc%20def'
Each part of a URL, e.g. the path info, the query, etc., has a
different set of reserved characters that must be quoted.
RFC 2396 Uniform Resource Identifiers (URI): Generic Syntax lists
the following reserved characters.
reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" |
"$" | ","
Each of these characters is reserved in some component of a URL,
but not necessarily in all of them.
By default, the quote function is intended for quoting the path
section of a URL. Thus, it will not encode '/'. This character
is reserved, but in typical usage the quote function is being
called on a path where the existing slash characters are used as
reserved characters.
string and safe may be either str or bytes objects. encoding must
not be specified if string is a str.
The optional encoding and errors parameters specify how to deal with
non-ASCII characters, as accepted by the str.encode method.
By default, encoding='utf-8' (characters are encoded with UTF-8), and
errors='strict' (unsupported characters raise a UnicodeEncodeError).
"""
if isinstance(string, str):
if not string:
return string
if encoding is None:
encoding = 'utf-8'
if errors is None:
errors = 'strict'
string = string.encode(encoding, errors)
else:
if encoding is not None:
raise TypeError("quote() doesn't support 'encoding' for bytes")
if errors is not None:
raise TypeError("quote() doesn't support 'errors' for bytes")
return quote_from_bytes(string, safe)
def quote_plus(string, safe='', encoding=None, errors=None):
"""Like quote(), but also replace ' ' with '+', as required for quoting
HTML form values. Plus signs in the original string are escaped unless
they are included in safe. It also does not have safe default to '/'.
"""
# Check if ' ' in string, where string may either be a str or bytes. If
# there are no spaces, the regular quote will produce the right answer.
if ((isinstance(string, str) and ' ' not in string) or
(isinstance(string, bytes) and b' ' not in string)):
return quote(string, safe, encoding, errors)
if isinstance(safe, str):
space = ' '
else:
space = b' '
string = quote(string, safe + space, encoding, errors)
return string.replace(' ', '+')
def quote_from_bytes(bs, safe='/'):
"""Like quote(), but accepts a bytes object rather than a str, and does
not perform string-to-bytes encoding. It always returns an ASCII string.
quote_from_bytes(b'abc def\xab') -> 'abc%20def%AB'
"""
if not isinstance(bs, (bytes, bytearray)):
raise TypeError("quote_from_bytes() expected bytes")
if not bs:
return ''
if isinstance(safe, str):
# Normalize 'safe' by converting to bytes and removing non-ASCII chars
safe = safe.encode('ascii', 'ignore')
else:
safe = bytes([c for c in safe if c < 128])
if not bs.rstrip(_ALWAYS_SAFE_BYTES + safe):
return bs.decode()
try:
quoter = _safe_quoters[safe]
except KeyError:
_safe_quoters[safe] = quoter = Quoter(safe).__getitem__
return ''.join([quoter(char) for char in bs])
def urlencode(query, doseq=False, safe='', encoding=None, errors=None):
"""Encode a sequence of two-element tuples or dictionary into a URL query string.
If any values in the query arg are sequences and doseq is true, each
sequence element is converted to a separate parameter.
If the query arg is a sequence of two-element tuples, the order of the
parameters in the output will match the order of parameters in the
input.
The query arg may be either a string or a bytes type. When query arg is a
string, the safe, encoding and error parameters are sent the quote_plus for
encoding.
"""
if hasattr(query, "items"):
query = query.items()
else:
# It's a bother at times that strings and string-like objects are
# sequences.
try:
# non-sequence items should not work with len()
# non-empty strings will fail this
if len(query) and not isinstance(query[0], tuple):
raise TypeError
# Zero-length sequences of all types will get here and succeed,
# but that's a minor nit. Since the original implementation
# allowed empty dicts that type of behavior probably should be
# preserved for consistency
except TypeError:
ty, va, tb = sys.exc_info()
raise TypeError("not a valid non-string sequence "
"or mapping object").with_traceback(tb)
l = []
if not doseq:
for k, v in query:
if isinstance(k, bytes):
k = quote_plus(k, safe)
else:
k = quote_plus(str(k), safe, encoding, errors)
if isinstance(v, bytes):
v = quote_plus(v, safe)
else:
v = quote_plus(str(v), safe, encoding, errors)
l.append(k + '=' + v)
else:
for k, v in query:
if isinstance(k, bytes):
k = quote_plus(k, safe)
else:
k = quote_plus(str(k), safe, encoding, errors)
if isinstance(v, bytes):
v = quote_plus(v, safe)
l.append(k + '=' + v)
elif isinstance(v, str):
v = quote_plus(v, safe, encoding, errors)
l.append(k + '=' + v)
else:
try:
# Is this a sufficient test for sequence-ness?
x = len(v)
except TypeError:
# not a sequence
v = quote_plus(str(v), safe, encoding, errors)
l.append(k + '=' + v)
else:
# loop over the sequence
for elt in v:
if isinstance(elt, bytes):
elt = quote_plus(elt, safe)
else:
elt = quote_plus(str(elt), safe, encoding, errors)
l.append(k + '=' + elt)
return '&'.join(l)
# Utilities to parse URLs (most of these return None for missing parts):
# unwrap('<URL:type://host/path>') --> 'type://host/path'
# splittype('type:opaquestring') --> 'type', 'opaquestring'
# splithost('//host[:port]/path') --> 'host[:port]', '/path'
# splituser('user[:passwd]@host[:port]') --> 'user[:passwd]', 'host[:port]'
# splitpasswd('user:passwd') -> 'user', 'passwd'
# splitport('host:port') --> 'host', 'port'
# splitquery('/path?query') --> '/path', 'query'
# splittag('/path#tag') --> '/path', 'tag'
# splitattr('/path;attr1=value1;attr2=value2;...') ->
# '/path', ['attr1=value1', 'attr2=value2', ...]
# splitvalue('attr=value') --> 'attr', 'value'
# urllib.parse.unquote('abc%20def') -> 'abc def'
# quote('abc def') -> 'abc%20def')
def to_bytes(url):
"""to_bytes(u"URL") --> 'URL'."""
# Most URL schemes require ASCII. If that changes, the conversion
# can be relaxed.
# XXX get rid of to_bytes()
if isinstance(url, str):
try:
url = url.encode("ASCII").decode()
except UnicodeError:
raise UnicodeError("URL " + repr(url) +
" contains non-ASCII characters")
return url
def unwrap(url):
"""unwrap('<URL:type://host/path>') --> 'type://host/path'."""
url = str(url).strip()
if url[:1] == '<' and url[-1:] == '>':
url = url[1:-1].strip()
if url[:4] == 'URL:': url = url[4:].strip()
return url
_typeprog = None
def splittype(url):
"""splittype('type:opaquestring') --> 'type', 'opaquestring'."""
global _typeprog
if _typeprog is None:
import re
_typeprog = re.compile('^([^/:]+):')
match = _typeprog.match(url)
if match:
scheme = match.group(1)
return scheme.lower(), url[len(scheme) + 1:]
return None, url
_hostprog = None
def splithost(url):
"""splithost('//host[:port]/path') --> 'host[:port]', '/path'."""
global _hostprog
if _hostprog is None:
import re
_hostprog = re.compile('^//([^/?]*)(.*)$')
match = _hostprog.match(url)
if match: return match.group(1, 2)
return None, url
_userprog = None
def splituser(host):
"""splituser('user[:passwd]@host[:port]') --> 'user[:passwd]', 'host[:port]'."""
global _userprog
if _userprog is None:
import re
_userprog = re.compile('^(.*)@(.*)$')
match = _userprog.match(host)
if match: return map(unquote, match.group(1, 2))
return None, host
_passwdprog = None
def splitpasswd(user):
"""splitpasswd('user:passwd') -> 'user', 'passwd'."""
global _passwdprog
if _passwdprog is None:
import re
_passwdprog = re.compile('^([^:]*):(.*)$',re.S)
match = _passwdprog.match(user)
if match: return match.group(1, 2)
return user, None
# splittag('/path#tag') --> '/path', 'tag'
_portprog = None
def splitport(host):
"""splitport('host:port') --> 'host', 'port'."""
global _portprog
if _portprog is None:
import re
_portprog = re.compile('^(.*):([0-9]+)$')
match = _portprog.match(host)
if match: return match.group(1, 2)
return host, None
_nportprog = None
def splitnport(host, defport=-1):
"""Split host and port, returning numeric port.
Return given default port if no ':' found; defaults to -1.
Return numerical port if a valid number are found after ':'.
Return None if ':' but not a valid number."""
global _nportprog
if _nportprog is None:
import re
_nportprog = re.compile('^(.*):(.*)$')
match = _nportprog.match(host)
if match:
host, port = match.group(1, 2)
try:
if not port: raise ValueError("no digits")
nport = int(port)
except ValueError:
nport = None
return host, nport
return host, defport
_queryprog = None
def splitquery(url):
"""splitquery('/path?query') --> '/path', 'query'."""
global _queryprog
if _queryprog is None:
import re
_queryprog = re.compile('^(.*)\?([^?]*)$')
match = _queryprog.match(url)
if match: return match.group(1, 2)
return url, None
_tagprog = None
def splittag(url):
"""splittag('/path#tag') --> '/path', 'tag'."""
global _tagprog
if _tagprog is None:
import re
_tagprog = re.compile('^(.*)#([^#]*)$')
match = _tagprog.match(url)
if match: return match.group(1, 2)
return url, None
def splitattr(url):
"""splitattr('/path;attr1=value1;attr2=value2;...') ->
'/path', ['attr1=value1', 'attr2=value2', ...]."""
words = url.split(';')
return words[0], words[1:]
_valueprog = None
def splitvalue(attr):
"""splitvalue('attr=value') --> 'attr', 'value'."""
global _valueprog
if _valueprog is None:
import re
_valueprog = re.compile('^([^=]*)=(.*)$')
match = _valueprog.match(attr)
if match: return match.group(1, 2)
return attr, None