Package lxml :: Module cssselect |
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# Source Code for Module lxml.cssselect

      1  """CSS Selectors based on XPath.
      2
      3  This module supports selecting XML/HTML tags based on CSS selectors.
      4  See the `CSSSelector` class for details.
      5  """
      6
      7  import re
      8  from lxml import etree
      9
     10  __all__ = ['SelectorSyntaxError', 'ExpressionError',
     11             'CSSSelector']
     12
     13  try:
     14      _basestring = basestring
     15  except NameError:
     16      _basestring = str
     17
     18 -class SelectorSyntaxError(SyntaxError):
     19      pass
     20
     21 -class ExpressionError(RuntimeError):
     22      pass
     23
     24 -class CSSSelector(etree.XPath):
     25      """A CSS selector.
     26
     27      Usage::
     28
     29          >>> from lxml import etree, cssselect
     30          >>> select = cssselect.CSSSelector("a tag > child")
     31
     32          >>> root = etree.XML("<a><b><c/><tag><child>TEXT</child></tag></b></a>")
     33          >>> [ el.tag for el in select(root) ]
     34          ['child']
     35      """
     36 -    def __init__(self, css):
     37          path = css_to_xpath(css)
     38          etree.XPath.__init__(self, path)
     39          self.css = css
     40
     41 -    def __repr__(self):
     42          return '<%s %s for %r>' % (
     43              self.__class__.__name__,
     44              hex(abs(id(self)))[2:],
     45              self.css)
     46
     47  ##############################
     48  ## Token objects:
     49
     50  try:
     51      _unicode = unicode
     52      _unichr = unichr
     53  except NameError:
     54      # Python 3
     55      _unicode = str
     56      _unichr = chr
     57
     58 -class _UniToken(_unicode):
     59 -    def __new__(cls, contents, pos):
     60          obj = _unicode.__new__(cls, contents)
     61          obj.pos = pos
     62          return obj
     63
     64 -    def __repr__(self):
     65          return '%s(%s, %r)' % (
     66              self.__class__.__name__,
     67              _unicode.__repr__(self),
     68              self.pos)
     69
     70 -class Symbol(_UniToken):
     71      pass
     72
     73 -class String(_UniToken):
     74      pass
     75
     76 -class Token(_UniToken):
     77      pass
     78
     79  ############################################################
     80  ## Parsing
     81  ############################################################
     82
     83  ##############################
     84  ## Syntax objects:
     85
     86 -class Class(object):
     87      """
     88      Represents selector.class_name
     89      """
     90
     91 -    def __init__(self, selector, class_name):
     92          self.selector = selector
     93          self.class_name = class_name
     94
     95 -    def __repr__(self):
     96          return '%s[%r.%s]' % (
     97              self.__class__.__name__,
     98              self.selector,
     99              self.class_name)
    100
    101 -    def xpath(self):
    102          sel_xpath = self.selector.xpath()
    103          sel_xpath.add_condition(
    104              "contains(concat(' ', normalize-space(@class), ' '), %s)" % xpath_literal(' '+self.class_name+' '))
    105          return sel_xpath
    106
    107 -class Function(object):
    108      """
    109      Represents selector:name(expr)
    110      """
    111
    112      unsupported = [
    113          'target', 'lang', 'enabled', 'disabled',]
    114
    115 -    def __init__(self, selector, type, name, expr):
    116          self.selector = selector
    117          self.type = type
    118          self.name = name
    119          self.expr = expr
    120
    121 -    def __repr__(self):
    122          return '%s[%r%s%s(%r)]' % (
    123              self.__class__.__name__,
    124              self.selector,
    125              self.type, self.name, self.expr)
    126
    127 -    def xpath(self):
    128          sel_path = self.selector.xpath()
    129          if self.name in self.unsupported:
    130              raise ExpressionError(
    131                  "The psuedo-class %r is not supported" % self.name)
    132          method = '_xpath_' + self.name.replace('-', '_')
    133          if not hasattr(self, method):
    134              raise ExpressionError(
    135                  "The psuedo-class %r is unknown" % self.name)
    136          method = getattr(self, method)
    137          return method(sel_path, self.expr)
    138
    139 -    def _xpath_nth_child(self, xpath, expr, last=False,
    140                           add_name_test=True):
    141          a, b = parse_series(expr)
    142          if not a and not b and not last:
    143              # a=0 means nothing is returned...
    144              xpath.add_condition('false() and position() = 0')
    145              return xpath
    146          if add_name_test:
    147              xpath.add_name_test()
    148          xpath.add_star_prefix()
    149          if a == 0:
    150              if last:
    151                  b = 'last() - %s' % b
    152              xpath.add_condition('position() = %s' % b)
    153              return xpath
    154          if last:
    155              # FIXME: I'm not sure if this is right
    156              a = -a
    157              b = -b
    158          if b > 0:
    159              b_neg = str(-b)
    160          else:
    161              b_neg = '+%s' % (-b)
    162          if a != 1:
    163              expr = ['(position() %s) mod %s = 0' % (b_neg, a)]
    164          else:
    165              expr = []
    166          if b >= 0:
    167              expr.append('position() >= %s' % b)
    168          elif b < 0 and last:
    169              expr.append('position() < (last() %s)' % b)
    170          expr = ' and '.join(expr)
    171          if expr:
    172              xpath.add_condition(expr)
    173          return xpath
    174          # FIXME: handle an+b, odd, even
    175          # an+b means every-a, plus b, e.g., 2n+1 means odd
    176          # 0n+b means b
    177          # n+0 means a=1, i.e., all elements
    178          # an means every a elements, i.e., 2n means even
    179          # -n means -1n
    180          # -1n+6 means elements 6 and previous
    181
    182 -    def _xpath_nth_last_child(self, xpath, expr):
    183          return self._xpath_nth_child(xpath, expr, last=True)
    184
    185 -    def _xpath_nth_of_type(self, xpath, expr):
    186          if xpath.element == '*':
    187              raise NotImplementedError(
    188                  "*:nth-of-type() is not implemented")
    189          return self._xpath_nth_child(xpath, expr, add_name_test=False)
    190
    191 -    def _xpath_nth_last_of_type(self, xpath, expr):
    192          return self._xpath_nth_child(xpath, expr, last=True, add_name_test=False)
    193
    194 -    def _xpath_contains(self, xpath, expr):
    195          # text content, minus tags, must contain expr
    196          if isinstance(expr, Element):
    197              expr = expr._format_element()
    198          xpath.add_condition('contains(css:lower-case(string(.)), %s)'
    199                              % xpath_literal(expr.lower()))
    200          # FIXME: Currently case insensitive matching doesn't seem to be happening
    201          return xpath
    202
    203 -    def _xpath_not(self, xpath, expr):
    204          # everything for which not expr applies
    205          expr = expr.xpath()
    206          cond = expr.condition
    207          # FIXME: should I do something about element_path?
    208          xpath.add_condition('not(%s)' % cond)
    209          return xpath
    210
    211 -def _make_lower_case(context, s):
    212      return s.lower()
    213
    214  ns = etree.FunctionNamespace('http://codespeak.net/lxml/css/')
    215  ns.prefix = 'css'
    216  ns['lower-case'] = _make_lower_case
    217
    218 -class Pseudo(object):
    219      """
    220      Represents selector:ident
    221      """
    222
    223      unsupported = ['indeterminate', 'first-line', 'first-letter',
    224                     'selection', 'before', 'after', 'link', 'visited',
    225                     'active', 'focus', 'hover']
    226
    227 -    def __init__(self, element, type, ident):
    228          self.element = element
    229          assert type in (':', '::')
    230          self.type = type
    231          self.ident = ident
    232
    233 -    def __repr__(self):
    234          return '%s[%r%s%s]' % (
    235              self.__class__.__name__,
    236              self.element,
    237              self.type, self.ident)
    238
    239 -    def xpath(self):
    240          el_xpath = self.element.xpath()
    241          if self.ident in self.unsupported:
    242              raise ExpressionError(
    243                  "The psuedo-class %r is unsupported" % self.ident)
    244          method = '_xpath_' + self.ident.replace('-', '_')
    245          if not hasattr(self, method):
    246              raise ExpressionError(
    247                  "The psuedo-class %r is unknown" % self.ident)
    248          method = getattr(self, method)
    249          el_xpath = method(el_xpath)
    250          return el_xpath
    251
    252 -    def _xpath_checked(self, xpath):
    253          # FIXME: is this really all the elements?
    254          xpath.add_condition("(@selected or @checked) and (name(.) = 'input' or name(.) = 'option')")
    255          return xpath
    256
    257 -    def _xpath_root(self, xpath):
    258          # if this element is the root element
    259          raise NotImplementedError
    260
    261 -    def _xpath_first_child(self, xpath):
    262          xpath.add_star_prefix()
    263          xpath.add_name_test()
    264          xpath.add_condition('position() = 1')
    265          return xpath
    266
    267 -    def _xpath_last_child(self, xpath):
    268          xpath.add_star_prefix()
    269          xpath.add_name_test()
    270          xpath.add_condition('position() = last()')
    271          return xpath
    272
    273 -    def _xpath_first_of_type(self, xpath):
    274          if xpath.element == '*':
    275              raise NotImplementedError(
    276                  "*:first-of-type is not implemented")
    277          xpath.add_star_prefix()
    278          xpath.add_condition('position() = 1')
    279          return xpath
    280
    281 -    def _xpath_last_of_type(self, xpath):
    282          if xpath.element == '*':
    283              raise NotImplementedError(
    284                  "*:last-of-type is not implemented")
    285          xpath.add_star_prefix()
    286          xpath.add_condition('position() = last()')
    287          return xpath
    288
    289 -    def _xpath_only_child(self, xpath):
    290          xpath.add_name_test()
    291          xpath.add_star_prefix()
    292          xpath.add_condition('last() = 1')
    293          return xpath
    294
    295 -    def _xpath_only_of_type(self, xpath):
    296          if xpath.element == '*':
    297              raise NotImplementedError(
    298                  "*:only-of-type is not implemented")
    299          xpath.add_condition('last() = 1')
    300          return xpath
    301
    302 -    def _xpath_empty(self, xpath):
    303          xpath.add_condition("not(*) and not(normalize-space())")
    304          return xpath
    305
    306 -class Attrib(object):
    307      """
    308      Represents selector[namespace|attrib operator value]
    309      """
    310
    311 -    def __init__(self, selector, namespace, attrib, operator, value):
    312          self.selector = selector
    313          self.namespace = namespace
    314          self.attrib = attrib
    315          self.operator = operator
    316          self.value = value
    317
    318 -    def __repr__(self):
    319          if self.operator == 'exists':
    320              return '%s[%r[%s]]' % (
    321                  self.__class__.__name__,
    322                  self.selector,
    323                  self._format_attrib())
    324          else:
    325              return '%s[%r[%s %s %r]]' % (
    326                  self.__class__.__name__,
    327                  self.selector,
    328                  self._format_attrib(),
    329                  self.operator,
    330                  self.value)
    331
    332 -    def _format_attrib(self):
    333          if self.namespace == '*':
    334              return self.attrib
    335          else:
    336              return '%s|%s' % (self.namespace, self.attrib)
    337
    338 -    def _xpath_attrib(self):
    339          # FIXME: if attrib is *?
    340          if self.namespace == '*':
    341              return '@' + self.attrib
    342          else:
    343              return '@%s:%s' % (self.namespace, self.attrib)
    344
    345 -    def xpath(self):
    346          path = self.selector.xpath()
    347          attrib = self._xpath_attrib()
    348          value = self.value
    349          if self.operator == 'exists':
    350              assert not value
    351              path.add_condition(attrib)
    352          elif self.operator == '=':
    353              path.add_condition('%s = %s' % (attrib,
    354                                              xpath_literal(value)))
    355          elif self.operator == '!=':
    356              # FIXME: this seems like a weird hack...
    357              if value:
    358                  path.add_condition('not(%s) or %s != %s'
    359                                     % (attrib, attrib, xpath_literal(value)))
    360              else:
    361                  path.add_condition('%s != %s'
    362                                     % (attrib, xpath_literal(value)))
    363              #path.add_condition('%s != %s' % (attrib, xpath_literal(value)))
    364          elif self.operator == '~=':
    365              path.add_condition("contains(concat(' ', normalize-space(%s), ' '), %s)" % (attrib, xpath_literal(' '+value+' ')))
    366          elif self.operator == '|=':
    367              # Weird, but true...
    368              path.add_condition('%s = %s or starts-with(%s, %s)' % (
    369                  attrib, xpath_literal(value),
    370                  attrib, xpath_literal(value + '-')))
    371          elif self.operator == '^=':
    372              path.add_condition('starts-with(%s, %s)' % (
    373                  attrib, xpath_literal(value)))
    374          elif self.operator == '$=':
    375              # Oddly there is a starts-with in XPath 1.0, but not ends-with
    376              path.add_condition('substring(%s, string-length(%s)-%s) = %s'
    377                                 % (attrib, attrib, len(value)-1, xpath_literal(value)))
    378          elif self.operator == '*=':
    379              # FIXME: case sensitive?
    380              path.add_condition('contains(%s, %s)' % (
    381                  attrib, xpath_literal(value)))
    382          else:
    383              assert 0, ("Unknown operator: %r" % self.operator)
    384          return path
    385
    386 -class Element(object):
    387      """
    388      Represents namespace|element
    389      """
    390
    391 -    def __init__(self, namespace, element):
    392          self.namespace = namespace
    393          self.element = element
    394
    395 -    def __repr__(self):
    396          return '%s[%s]' % (
    397              self.__class__.__name__,
    398              self._format_element())
    399
    400 -    def _format_element(self):
    401          if self.namespace == '*':
    402              return self.element
    403          else:
    404              return '%s|%s' % (self.namespace, self.element)
    405
    406 -    def xpath(self):
    407          if self.namespace == '*':
    408              el = self.element.lower()
    409          else:
    410              # FIXME: Should we lowercase here?
    411              el = '%s:%s' % (self.namespace, self.element)
    412          return XPathExpr(element=el)
    413
    414 -class Hash(object):
    415      """
    416      Represents selector#id
    417      """
    418
    419 -    def __init__(self, selector, id):
    420          self.selector = selector
    421          self.id = id
    422
    423 -    def __repr__(self):
    424          return '%s[%r#%s]' % (
    425              self.__class__.__name__,
    426              self.selector, self.id)
    427
    428 -    def xpath(self):
    429          path = self.selector.xpath()
    430          path.add_condition('@id = %s' % xpath_literal(self.id))
    431          return path
    432
    433 -class Or(object):
    434
    435 -    def __init__(self, items):
    436          self.items = items
    437 -    def __repr__(self):
    438          return '%s(%r)' % (
    439              self.__class__.__name__,
    440              self.items)
    441
    442 -    def xpath(self):
    443          paths = [item.xpath() for item in self.items]
    444          return XPathExprOr(paths)
    445
    446 -class CombinedSelector(object):
    447
    448      _method_mapping = {
    449          ' ': 'descendant',
    450          '>': 'child',
    451          '+': 'direct_adjacent',
    452          '~': 'indirect_adjacent',
    453          }
    454
    455 -    def __init__(self, selector, combinator, subselector):
    456          assert selector is not None
    457          self.selector = selector
    458          self.combinator = combinator
    459          self.subselector = subselector
    460
    461 -    def __repr__(self):
    462          if self.combinator == ' ':
    463              comb = '<followed>'
    464          else:
    465              comb = self.combinator
    466          return '%s[%r %s %r]' % (
    467              self.__class__.__name__,
    468              self.selector,
    469              comb,
    470              self.subselector)
    471
    472 -    def xpath(self):
    473          if self.combinator not in self._method_mapping:
    474              raise ExpressionError(
    475                  "Unknown combinator: %r" % self.combinator)
    476          method = '_xpath_' + self._method_mapping[self.combinator]
    477          method = getattr(self, method)
    478          path = self.selector.xpath()
    479          return method(path, self.subselector)
    480
    481 -    def _xpath_descendant(self, xpath, sub):
    482          # when sub is a descendant in any way of xpath
    483          xpath.join('/descendant::', sub.xpath())
    484          return xpath
    485
    486 -    def _xpath_child(self, xpath, sub):
    487          # when sub is an immediate child of xpath
    488          xpath.join('/', sub.xpath())
    489          return xpath
    490
    491 -    def _xpath_direct_adjacent(self, xpath, sub):
    492          # when sub immediately follows xpath
    493          xpath.join('/following-sibling::', sub.xpath())
    494          xpath.add_name_test()
    495          xpath.add_condition('position() = 1')
    496          return xpath
    497
    498 -    def _xpath_indirect_adjacent(self, xpath, sub):
    499          # when sub comes somewhere after xpath as a sibling
    500          xpath.join('/following-sibling::', sub.xpath())
    501          return xpath
    502
    503  ##############################
    504  ## XPathExpr objects:
    505
    506  _el_re = re.compile(r'^\w+\s*$', re.UNICODE)
    507  _id_re = re.compile(r'^(\w*)#(\w+)\s*$', re.UNICODE)
    508  _class_re = re.compile(r'^(\w*)\.(\w+)\s*$', re.UNICODE)
    509
    510 -def css_to_xpath(css_expr, prefix='descendant-or-self::'):
    511      if isinstance(css_expr, _basestring):
    512          match = _el_re.search(css_expr)
    513          if match is not None:
    514              return '%s%s' % (prefix, match.group(0).strip())
    515          match = _id_re.search(css_expr)
    516          if match is not None:
    517              return "%s%s[@id = '%s']" % (
    518                  prefix, match.group(1) or '*', match.group(2))
    519          match = _class_re.search(css_expr)
    520          if match is not None:
    521              return "%s%s[contains(concat(' ', normalize-space(@class), ' '), ' %s ')]" % (
    522                  prefix, match.group(1) or '*', match.group(2))
    523          css_expr = parse(css_expr)
    524      expr = css_expr.xpath()
    525      assert expr is not None, (
    526          "Got None for xpath expression from %s" % repr(css_expr))
    527      if prefix:
    528          expr.add_prefix(prefix)
    529      return _unicode(expr)
    530
    531 -class XPathExpr(object):
    532
    533 -    def __init__(self, prefix=None, path=None, element='*', condition=None,
    534                   star_prefix=False):
    535          self.prefix = prefix
    536          self.path = path
    537          self.element = element
    538          self.condition = condition
    539          self.star_prefix = star_prefix
    540
    541 -    def __str__(self):
    542          path = ''
    543          if self.prefix is not None:
    544              path += _unicode(self.prefix)
    545          if self.path is not None:
    546              path += _unicode(self.path)
    547          path += _unicode(self.element)
    548          if self.condition:
    549              path += '[%s]' % self.condition
    550          return path
    551
    552 -    def __repr__(self):
    553          return '%s[%s]' % (
    554              self.__class__.__name__, self)
    555
    556 -    def add_condition(self, condition):
    557          if self.condition:
    558              self.condition = '%s and (%s)' % (self.condition, condition)
    559          else:
    560              self.condition = condition
    561
    562 -    def add_path(self, part):
    563          if self.path is None:
    564              self.path = self.element
    565          else:
    566              self.path += self.element
    567          self.element = part
    568
    569 -    def add_prefix(self, prefix):
    570          if self.prefix:
    571              self.prefix = prefix + self.prefix
    572          else:
    573              self.prefix = prefix
    574
    575 -    def add_name_test(self):
    576          if self.element == '*':
    577              # We weren't doing a test anyway
    578              return
    579          self.add_condition("name() = %s" % xpath_literal(self.element))
    580          self.element = '*'
    581
    582 -    def add_star_prefix(self):
    583          """
    584          Adds a /* prefix if there is no prefix.  This is when you need
    585          to keep context's constrained to a single parent.
    586          """
    587          if self.path:
    588              self.path += '*/'
    589          else:
    590              self.path = '*/'
    591          self.star_prefix = True
    592
    593 -    def join(self, combiner, other):
    594          prefix = _unicode(self)
    595          prefix += combiner
    596          path = (other.prefix or '') + (other.path or '')
    597          # We don't need a star prefix if we are joining to this other
    598          # prefix; so we'll get rid of it
    599          if other.star_prefix and path == '*/':
    600              path = ''
    601          self.prefix = prefix
    602          self.path = path
    603          self.element = other.element
    604          self.condition = other.condition
    605
    606 -class XPathExprOr(XPathExpr):
    607      """
    608      Represents |'d expressions.  Note that unfortunately it isn't
    609      the union, it's the sum, so duplicate elements will appear.
    610      """
    611
    612 -    def __init__(self, items, prefix=None):
    613          for item in items:
    614              assert item is not None
    615          self.items = items
    616          self.prefix = prefix
    617
    618 -    def __str__(self):
    619          prefix = self.prefix or ''
    620          return ' | '.join(["%s%s" % (prefix,i) for i in self.items])
    621
    622  split_at_single_quotes = re.compile("('+)").split
    623
    624 -def xpath_literal(s):
    625      if isinstance(s, Element):
    626          # This is probably a symbol that looks like an expression...
    627          s = s._format_element()
    628      else:
    629          s = _unicode(s)
    630      if "'" not in s:
    631          s = "'%s'" % s
    632      elif '"' not in s:
    633          s = '"%s"' % s
    634      else:
    635          s = "concat(%s)" % ','.join([
    636              (("'" in part) and '"%s"' or "'%s'") % part
    637              for part in split_at_single_quotes(s) if part
    638              ])
    639      return s
    640
    641  ##############################
    642  ## Parsing functions
    643
    644 -def parse(string):
    645      stream = TokenStream(tokenize(string))
    646      stream.source = string
    647      try:
    648          return parse_selector_group(stream)
    649      except SelectorSyntaxError:
    650          import sys
    651          e = sys.exc_info()[1]
    652          message = "%s at %s -> %r" % (
    653              e, stream.used, stream.peek())
    654          e.msg = message
    655          if sys.version_info < (2,6):
    656              e.message = message
    657          e.args = tuple([message])
    658          raise
    659
    660 -def parse_selector_group(stream):
    661      result = []
    662      while 1:
    663          result.append(parse_selector(stream))
    664          if stream.peek() == ',':
    665              stream.next()
    666          else:
    667              break
    668      if len(result) == 1:
    669          return result[0]
    670      else:
    671          return Or(result)
    672
    673 -def parse_selector(stream):
    674      result = parse_simple_selector(stream)
    675      while 1:
    676          peek = stream.peek()
    677          if peek == ',' or peek is None:
    678              return result
    679          elif peek in ('+', '>', '~'):
    680              # A combinator
    681              combinator = stream.next()
    682          else:
    683              combinator = ' '
    684          consumed = len(stream.used)
    685          next_selector = parse_simple_selector(stream)
    686          if consumed == len(stream.used):
    687              raise SelectorSyntaxError(
    688                  "Expected selector, got '%s'" % stream.peek())
    689          result = CombinedSelector(result, combinator, next_selector)
    690      return result
    691
    692 -def parse_simple_selector(stream):
    693      peek = stream.peek()
    694      if peek != '*' and not isinstance(peek, Symbol):
    695          element = namespace = '*'
    696      else:
    697          next = stream.next()
    698          if next != '*' and not isinstance(next, Symbol):
    699              raise SelectorSyntaxError(
    700                  "Expected symbol, got '%s'" % next)
    701          if stream.peek() == '|':
    702              namespace = next
    703              stream.next()
    704              element = stream.next()
    705              if element != '*' and not isinstance(next, Symbol):
    706                  raise SelectorSyntaxError(
    707                      "Expected symbol, got '%s'" % next)
    708          else:
    709              namespace = '*'
    710              element = next
    711      result = Element(namespace, element)
    712      has_hash = False
    713      while 1:
    714          peek = stream.peek()
    715          if peek == '#':
    716              if has_hash:
    717                  # You can't have two hashes
    718                  # (FIXME: is there some more general rule I'm missing?)
    719                  break
    720              stream.next()
    721              result = Hash(result, stream.next())
    722              has_hash = True
    723              continue
    724          elif peek == '.':
    725              stream.next()
    726              result = Class(result, stream.next())
    727              continue
    728          elif peek == '[':
    729              stream.next()
    730              result = parse_attrib(result, stream)
    731              next = stream.next()
    732              if not next == ']':
    733                  raise SelectorSyntaxError(
    734                      "] expected, got '%s'" % next)
    735              continue
    736          elif peek == ':' or peek == '::':
    737              type = stream.next()
    738              ident = stream.next()
    739              if not isinstance(ident, Symbol):
    740                  raise SelectorSyntaxError(
    741                      "Expected symbol, got '%s'" % ident)
    742              if stream.peek() == '(':
    743                  stream.next()
    744                  peek = stream.peek()
    745                  if isinstance(peek, String):
    746                      selector = stream.next()
    747                  elif isinstance(peek, Symbol) and is_int(peek):
    748                      selector = int(stream.next())
    749                  else:
    750                      # FIXME: parse_simple_selector, or selector, or...?
    751                      selector = parse_simple_selector(stream)
    752                  next = stream.next()
    753                  if not next == ')':
    754                      raise SelectorSyntaxError(
    755                          "Expected ')', got '%s' and '%s'"
    756                          % (next, selector))
    757                  result = Function(result, type, ident, selector)
    758              else:
    759                  result = Pseudo(result, type, ident)
    760              continue
    761          else:
    762              if peek == ' ':
    763                  stream.next()
    764              break
    765          # FIXME: not sure what "negation" is
    766      return result
    767
    768 -def is_int(v):
    769      try:
    770          int(v)
    771      except ValueError:
    772          return False
    773      else:
    774          return True
    775
    776 -def parse_attrib(selector, stream):
    777      attrib = stream.next()
    778      if stream.peek() == '|':
    779          namespace = attrib
    780          stream.next()
    781          attrib = stream.next()
    782      else:
    783          namespace = '*'
    784      if stream.peek() == ']':
    785          return Attrib(selector, namespace, attrib, 'exists', None)
    786      op = stream.next()
    787      if not op in ('^=', '$=', '*=', '=', '~=', '|=', '!='):
    788          raise SelectorSyntaxError(
    789              "Operator expected, got '%s'" % op)
    790      value = stream.next()
    791      if not isinstance(value, (Symbol, String)):
    792          raise SelectorSyntaxError(
    793              "Expected string or symbol, got '%s'" % value)
    794      return Attrib(selector, namespace, attrib, op, value)
    795
    796 -def parse_series(s):
    797      """
    798      Parses things like '1n+2', or 'an+b' generally, returning (a, b)
    799      """
    800      if isinstance(s, Element):
    801          s = s._format_element()
    802      if not s or s == '*':
    803          # Happens when there's nothing, which the CSS parser thinks of as *
    804          return (0, 0)
    805      if isinstance(s, int):
    806          # Happens when you just get a number
    807          return (0, s)
    808      if s == 'odd':
    809          return (2, 1)
    810      elif s == 'even':
    811          return (2, 0)
    812      elif s == 'n':
    813          return (1, 0)
    814      if 'n' not in s:
    815          # Just a b
    816          return (0, int(s))
    817      a, b = s.split('n', 1)
    818      if not a:
    819          a = 1
    820      elif a == '-' or a == '+':
    821          a = int(a+'1')
    822      else:
    823          a = int(a)
    824      if not b:
    825          b = 0
    826      elif b == '-' or b == '+':
    827          b = int(b+'1')
    828      else:
    829          b = int(b)
    830      return (a, b)
    831
    832
    833  ############################################################
    834  ## Tokenizing
    835  ############################################################
    836
    837  _whitespace_re = re.compile(r'\s+', re.UNICODE)
    838
    839  _comment_re = re.compile(r'/\*.*?\*/', re.DOTALL)
    840
    841  _count_re = re.compile(r'[+-]?\d*n(?:[+-]\d+)?')
    842
    843 -def tokenize(s):
    844      pos = 0
    845      s = _comment_re.sub('', s)
    846      while 1:
    847          match = _whitespace_re.match(s, pos=pos)
    848          if match:
    849              preceding_whitespace_pos = pos
    850              pos = match.end()
    851          else:
    852              preceding_whitespace_pos = 0
    853          if pos >= len(s):
    854              return
    855          match = _count_re.match(s, pos=pos)
    856          if match and match.group() != 'n':
    857              sym = s[pos:match.end()]
    858              yield Symbol(sym, pos)
    859              pos = match.end()
    860              continue
    861          c = s[pos]
    862          c2 = s[pos:pos+2]
    863          if c2 in ('~=', '|=', '^=', '$=', '*=', '::', '!='):
    864              yield Token(c2, pos)
    865              pos += 2
    866              continue
    867          if c in '>+~,.*=[]()|:#':
    868              if c in '.#' and preceding_whitespace_pos > 0:
    869                  yield Token(' ', preceding_whitespace_pos)
    870              yield Token(c, pos)
    871              pos += 1
    872              continue
    873          if c == '"' or c == "'":
    874              # Quoted string
    875              old_pos = pos
    876              sym, pos = tokenize_escaped_string(s, pos)
    877              yield String(sym, old_pos)
    878              continue
    879          old_pos = pos
    880          sym, pos = tokenize_symbol(s, pos)
    881          yield Symbol(sym, old_pos)
    882          continue
    883
    884  split_at_string_escapes = re.compile(r'(\\(?:%s))'
    885                                       % '|'.join(['[A-Fa-f0-9]{1,6}(?:\r\n|\s)?',
    886                                                   '[^A-Fa-f0-9]'])).split
    887
    888 -def unescape_string_literal(literal):
    889      substrings = []
    890      for substring in split_at_string_escapes(literal):
    891          if not substring:
    892              continue
    893          elif '\\' in substring:
    894              if substring[0] == '\\' and len(substring) > 1:
    895                  substring = substring[1:]
    896                  if substring[0] in '0123456789ABCDEFabcdef':
    897                      # int() correctly ignores the potentially trailing whitespace
    898                      substring = _unichr(int(substring, 16))
    899              else:
    900                  raise SelectorSyntaxError(
    901                      "Invalid escape sequence %r in string %r"
    902                      % (substring.split('\\')[1], literal))
    903          substrings.append(substring)
    904      return ''.join(substrings)
    905
    906 -def tokenize_escaped_string(s, pos):
    907      quote = s[pos]
    908      assert quote in ('"', "'")
    909      pos = pos+1
    910      start = pos
    911      while 1:
    912          next = s.find(quote, pos)
    913          if next == -1:
    914              raise SelectorSyntaxError(
    915                  "Expected closing %s for string in: %r"
    916                  % (quote, s[start:]))
    917          result = s[start:next]
    918          if result.endswith('\\'):
    919              # next quote character is escaped
    920              pos = next+1
    921              continue
    922          if '\\' in result:
    923              result = unescape_string_literal(result)
    924          return result, next+1
    925
    926  _illegal_symbol = re.compile(r'[^\w\\-]', re.UNICODE)
    927
    928 -def tokenize_symbol(s, pos):
    929      start = pos
    930      match = _illegal_symbol.search(s, pos=pos)
    931      if not match:
    932          # Goes to end of s
    933          return s[start:], len(s)
    934      if match.start() == pos:
    935          assert 0, (
    936              "Unexpected symbol: %r at %s" % (s[pos], pos))
    937      if not match:
    938          result = s[start:]
    939          pos = len(s)
    940      else:
    941          result = s[start:match.start()]
    942          pos = match.start()
    943      try:
    944          result = result.encode('ASCII', 'backslashreplace').decode('unicode_escape')
    945      except UnicodeDecodeError:
    946          import sys
    947          e = sys.exc_info()[1]
    948          raise SelectorSyntaxError(
    949              "Bad symbol %r: %s" % (result, e))
    950      return result, pos
    951
    952 -class TokenStream(object):
    953
    954 -    def __init__(self, tokens, source=None):
    955          self.used = []
    956          self.tokens = iter(tokens)
    957          self.source = source
    958          self.peeked = None
    959          self._peeking = False
    960          try:
    961              self.next_token = self.tokens.next
    962          except AttributeError:
    963              # Python 3
    964              self.next_token = self.tokens.__next__
    965
    966 -    def next(self):
    967          if self._peeking:
    968              self._peeking = False
    969              self.used.append(self.peeked)
    970              return self.peeked
    971          else:
    972              try:
    973                  next = self.next_token()
    974                  self.used.append(next)
    975                  return next
    976              except StopIteration:
    977                  return None
    978
    979 -    def __iter__(self):
    980          return iter(self.next, None)
    981
    982 -    def peek(self):
    983          if not self._peeking:
    984              try:
    985                  self.peeked = self.next_token()
    986              except StopIteration:
    987                  return None
    988              self._peeking = True
    989          return self.peeked
    990