text: # Use of this source code is governed by a BSD-style license that can be
  # found in the LICENSE file.
  __license__ = "MIT"
  
  import collections
  import re
  import shlex
  import sys
  import warnings
  from bs4.dammit import EntitySubstitution
  
  DEFAULT_OUTPUT_ENCODING = "utf-8"
  PY3K = (sys.version_info[0] > 2)
  
  whitespace_re = re.compile("\s+")
  
  def _alias(attr):
      """Alias one attribute name to another for backward compatibility"""
      @property
      def alias(self):
          return getattr(self, attr)
  
      @alias.setter
      def alias(self):
          return setattr(self, attr)
      return alias
  
  
  class NamespacedAttribute(str):
  
      def __new__(cls, prefix, name, namespace=None):
          if name is None:
              obj = str.__new__(cls, prefix)
          elif prefix is None:
              # Not really namespaced.
              obj = str.__new__(cls, name)
          else:
              obj = str.__new__(cls, prefix + ":" + name)
          obj.prefix = prefix
          obj.name = name
          obj.namespace = namespace
          return obj
  
  class AttributeValueWithCharsetSubstitution(str):
      """A stand-in object for a character encoding specified in HTML."""
  
  class CharsetMetaAttributeValue(AttributeValueWithCharsetSubstitution):
      """A generic stand-in for the value of a meta tag's 'charset' attribute.
      When Beautiful Soup parses the markup '<meta charset="utf8">', the
      value of the 'charset' attribute will be one of these objects.
      """
  
      def __new__(cls, original_value):
          obj = str.__new__(cls, original_value)
          obj.original_value = original_value
          return obj
  
      def encode(self, encoding):
          return encoding
  
  
  class ContentMetaAttributeValue(AttributeValueWithCharsetSubstitution):
      """A generic stand-in for the value of a meta tag's 'content' attribute.
      When Beautiful Soup parses the markup:
       <meta http-equiv="content-type" content="text/html; charset=utf8">
      The value of the 'content' attribute will be one of these objects.
      """
  
      CHARSET_RE = re.compile("((^|;)\s*charset=)([^;]*)", re.M)
  
      def __new__(cls, original_value):
          match = cls.CHARSET_RE.search(original_value)
          if match is None:
              # No substitution necessary.
              return str.__new__(str, original_value)
  
          obj = str.__new__(cls, original_value)
          obj.original_value = original_value
          return obj
  
      def encode(self, encoding):
          def rewrite(match):
              return match.group(1) + encoding
          return self.CHARSET_RE.sub(rewrite, self.original_value)
  
  class HTMLAwareEntitySubstitution(EntitySubstitution):
  
      """Entity substitution rules that are aware of some HTML quirks.
      Specifically, the contents of <script> and <style> tags should not
      undergo entity substitution.
      Incoming NavigableString objects are checked to see if they're the
      direct children of a <script> or <style> tag.
      """
  
      cdata_containing_tags = set(["script", "style"])
  
      preformatted_tags = set(["pre"])
  
      preserve_whitespace_tags = set(['pre', 'textarea'])
  
      @classmethod
      def _substitute_if_appropriate(cls, ns, f):
          if (isinstance(ns, NavigableString)
              and ns.parent is not None
              and ns.parent.name in cls.cdata_containing_tags):
              # Do nothing.
              return ns
          # Substitute.
          return f(ns)
  
      @classmethod
      def substitute_html(cls, ns):
          return cls._substitute_if_appropriate(
              ns, EntitySubstitution.substitute_html)
  
      @classmethod
      def substitute_xml(cls, ns):
          return cls._substitute_if_appropriate(
              ns, EntitySubstitution.substitute_xml)
  
  class PageElement(object):
      """Contains the navigational information for some part of the page
      (either a tag or a piece of text)"""
  
      # There are five possible values for the "formatter" argument passed in
      # to methods like encode() and prettify():
      #
      # "html" - All Unicode characters with corresponding HTML entities
      #   are converted to those entities on output.
      # "minimal" - Bare ampersands and angle brackets are converted to
      #   XML entities: &amp; &lt; &gt;
      # None - The null formatter. Unicode characters are never
      #   converted to entities.  This is not recommended, but it's
      #   faster than "minimal".
      # A function - This function will be called on every string that
      #  needs to undergo entity substitution.
      #
  
      # In an HTML document, the default "html" and "minimal" functions
      # will leave the contents of <script> and <style> tags alone. For
      # an XML document, all tags will be given the same treatment.
  
      HTML_FORMATTERS = {
          "html" : HTMLAwareEntitySubstitution.substitute_html,
          "minimal" : HTMLAwareEntitySubstitution.substitute_xml,
          None : None
          }
  
      XML_FORMATTERS = {
          "html" : EntitySubstitution.substitute_html,
          "minimal" : EntitySubstitution.substitute_xml,
          None : None
          }
  
      def format_string(self, s, formatter='minimal'):
          """Format the given string using the given formatter."""
          if not isinstance(formatter, collections.Callable):
              formatter = self._formatter_for_name(formatter)
          if formatter is None:
              output = s
          else:
              output = formatter(s)
          return output
  
      @property
      def _is_xml(self):
          """Is this element part of an XML tree or an HTML tree?
          This is used when mapping a formatter name ("minimal") to an
          appropriate function (one that performs entity-substitution on
          the contents of <script> and <style> tags, or not). It can be
          inefficient, but it should be called very rarely.
          """
          if self.known_xml is not None:
              # Most of the time we will have determined this when the
              # document is parsed.
              return self.known_xml
  
          # Otherwise, it's likely that this element was created by
          # direct invocation of the constructor from within the user's
          # Python code.
          if self.parent is None:
              # This is the top-level object. It should have .known_xml set
              # from tree creation. If not, take a guess--BS is usually
              # used on HTML markup.
              return getattr(self, 'is_xml', False)
          return self.parent._is_xml
  
      def _formatter_for_name(self, name):
          "Look up a formatter function based on its name and the tree."
          if self._is_xml:
              return self.XML_FORMATTERS.get(
                  name, EntitySubstitution.substitute_xml)
          else:
              return self.HTML_FORMATTERS.get(
                  name, HTMLAwareEntitySubstitution.substitute_xml)
  
      def setup(self, parent=None, previous_element=None, next_element=None,
                previous_sibling=None, next_sibling=None):
          """Sets up the initial relations between this element and
          other elements."""
          self.parent = parent
  
          self.previous_element = previous_element
          if previous_element is not None:
              self.previous_element.next_element = self
  
          self.next_element = next_element
          if self.next_element:
              self.next_element.previous_element = self
  
          self.next_sibling = next_sibling
          if self.next_sibling:
              self.next_sibling.previous_sibling = self
  
          if (not previous_sibling
              and self.parent is not None and self.parent.contents):
              previous_sibling = self.parent.contents[-1]
  
          self.previous_sibling = previous_sibling
          if previous_sibling:
              self.previous_sibling.next_sibling = self
  
      nextSibling = _alias("next_sibling")  # BS3
      previousSibling = _alias("previous_sibling")  # BS3
  
      def replace_with(self, replace_with):
          if not self.parent:
              raise ValueError(
                  "Cannot replace one element with another when the"
                  "element to be replaced is not part of a tree.")
          if replace_with is self:
              return
          if replace_with is self.parent:
              raise ValueError("Cannot replace a Tag with its parent.")
          old_parent = self.parent
          my_index = self.parent.index(self)
          self.extract()
          old_parent.insert(my_index, replace_with)
          return self
      replaceWith = replace_with  # BS3
  
      def unwrap(self):
          my_parent = self.parent
          if not self.parent:
              raise ValueError(
                  "Cannot replace an element with its contents when that"
                  "element is not part of a tree.")
          my_index = self.parent.index(self)
          self.extract()
          for child in reversed(self.contents[:]):
              my_parent.insert(my_index, child)
          return self
      replace_with_children = unwrap
      replaceWithChildren = unwrap  # BS3
  
      def wrap(self, wrap_inside):
          me = self.replace_with(wrap_inside)
          wrap_inside.append(me)
          return wrap_inside
  
      def extract(self):
          """Destructively rips this element out of the tree."""
          if self.parent is not None:
              del self.parent.contents[self.parent.index(self)]
  
          #Find the two elements that would be next to each other if
          #this element (and any children) hadn't been parsed. Connect
          #the two.
          last_child = self._last_descendant()
          next_element = last_child.next_element
  
          if (self.previous_element is not None and
              self.previous_element is not next_element):
              self.previous_element.next_element = next_element
          if next_element is not None and next_element is not self.previous_element:
              next_element.previous_element = self.previous_element
          self.previous_element = None
          last_child.next_element = None
  
          self.parent = None
          if (self.previous_sibling is not None
              and self.previous_sibling is not self.next_sibling):
              self.previous_sibling.next_sibling = self.next_sibling
          if (self.next_sibling is not None
              and self.next_sibling is not self.previous_sibling):
              self.next_sibling.previous_sibling = self.previous_sibling
          self.previous_sibling = self.next_sibling = None
          return self
  
      def _last_descendant(self, is_initialized=True, accept_self=True):
          "Finds the last element beneath this object to be parsed."
          if is_initialized and self.next_sibling:
              last_child = self.next_sibling.previous_element
          else:
              last_child = self
              while isinstance(last_child, Tag) and last_child.contents:
                  last_child = last_child.contents[-1]
          if not accept_self and last_child is self:
              last_child = None
          return last_child
      # BS3: Not part of the API!
      _lastRecursiveChild = _last_descendant
  
      def insert(self, position, new_child):
          if new_child is None:
              raise ValueError("Cannot insert None into a tag.")
          if new_child is self:
              raise ValueError("Cannot insert a tag into itself.")
          if (isinstance(new_child, str)
              and not isinstance(new_child, NavigableString)):
              new_child = NavigableString(new_child)
  
          position = min(position, len(self.contents))
          if hasattr(new_child, 'parent') and new_child.parent is not None:
              # We're 'inserting' an element that's already one
              # of this object's children.
              if new_child.parent is self:
                  current_index = self.index(new_child)
                  if current_index < position:
                      # We're moving this element further down the list
                      # of this object's children. That means that when
                      # we extract this element, our target index will
                      # jump down one.
                      position -= 1
              new_child.extract()
  
          new_child.parent = self
          previous_child = None
          if position == 0:
              new_child.previous_sibling = None
              new_child.previous_element = self
          else:
              previous_child = self.contents[position - 1]
              new_child.previous_sibling = previous_child
              new_child.previous_sibling.next_sibling = new_child
              new_child.previous_element = previous_child._last_descendant(False)
          if new_child.previous_element is not None:
              new_child.previous_element.next_element = new_child
  
          new_childs_last_element = new_child._last_descendant(False)
  
          if position >= len(self.contents):
              new_child.next_sibling = None
  
              parent = self
              parents_next_sibling = None
              while parents_next_sibling is None and parent is not None:
                  parents_next_sibling = parent.next_sibling
                  parent = parent.parent
                  if parents_next_sibling is not None:
                      # We found the element that comes next in the document.
                      break
              if parents_next_sibling is not None:
                  new_childs_last_element.next_element = parents_next_sibling
              else:
                  # The last element of this tag is the last element in
                  # the document.
                  new_childs_last_element.next_element = None
          else:
              next_child = self.contents[position]
              new_child.next_sibling = next_child
              if new_child.next_sibling is not None:
                  new_child.next_sibling.previous_sibling = new_child
              new_childs_last_element.next_element = next_child
  
          if new_childs_last_element.next_element is not None:
              new_childs_last_element.next_element.previous_element = new_childs_last_element
          self.contents.insert(position, new_child)
  
      def append(self, tag):
          """Appends the given tag to the contents of this tag."""
          self.insert(len(self.contents), tag)
  
      def insert_before(self, predecessor):
          """Makes the given element the immediate predecessor of this one.
          The two elements will have the same parent, and the given element
          will be immediately before this one.
          """
          if self is predecessor:
              raise ValueError("Can't insert an element before itself.")
          parent = self.parent
          if parent is None:
              raise ValueError(
                  "Element has no parent, so 'before' has no meaning.")
          # Extract first so that the index won't be screwed up if they
          # are siblings.
          if isinstance(predecessor, PageElement):
              predecessor.extract()
          index = parent.index(self)
          parent.insert(index, predecessor)
  
      def insert_after(self, successor):
          """Makes the given element the immediate successor of this one.
          The two elements will have the same parent, and the given element
          will be immediately after this one.
          """
          if self is successor:
              raise ValueError("Can't insert an element after itself.")
          parent = self.parent
          if parent is None:
              raise ValueError(
                  "Element has no parent, so 'after' has no meaning.")
          # Extract first so that the index won't be screwed up if they
          # are siblings.
          if isinstance(successor, PageElement):
              successor.extract()
          index = parent.index(self)
          parent.insert(index+1, successor)
  
      def find_next(self, name=None, attrs={}, text=None, **kwargs):
          """Returns the first item that matches the given criteria and
          appears after this Tag in the document."""
          return self._find_one(self.find_all_next, name, attrs, text, **kwargs)
      findNext = find_next  # BS3
  
      def find_all_next(self, name=None, attrs={}, text=None, limit=None,
                      **kwargs):
          """Returns all items that match the given criteria and appear
          after this Tag in the document."""
          return self._find_all(name, attrs, text, limit, self.next_elements,
                               **kwargs)
      findAllNext = find_all_next  # BS3
  
      def find_next_sibling(self, name=None, attrs={}, text=None, **kwargs):
          """Returns the closest sibling to this Tag that matches the
          given criteria and appears after this Tag in the document."""
          return self._find_one(self.find_next_siblings, name, attrs, text,
                               **kwargs)
      findNextSibling = find_next_sibling  # BS3
  
      def find_next_siblings(self, name=None, attrs={}, text=None, limit=None,
                             **kwargs):
          """Returns the siblings of this Tag that match the given
          criteria and appear after this Tag in the document."""
          return self._find_all(name, attrs, text, limit,
                                self.next_siblings, **kwargs)
      findNextSiblings = find_next_siblings   # BS3
      fetchNextSiblings = find_next_siblings  # BS2
  
      def find_previous(self, name=None, attrs={}, text=None, **kwargs):
          """Returns the first item that matches the given criteria and
          appears before this Tag in the document."""
          return self._find_one(
              self.find_all_previous, name, attrs, text, **kwargs)
      findPrevious = find_previous  # BS3
  
      def find_all_previous(self, name=None, attrs={}, text=None, limit=None,
                          **kwargs):
          """Returns all items that match the given criteria and appear
          before this Tag in the document."""
          return self._find_all(name, attrs, text, limit, self.previous_elements,
                             **kwargs)
      findAllPrevious = find_all_previous  # BS3
      fetchPrevious = find_all_previous    # BS2
  
      def find_previous_sibling(self, name=None, attrs={}, text=None, **kwargs):
          """Returns the closest sibling to this Tag that matches the
          given criteria and appears before this Tag in the document."""
          return self._find_one(self.find_previous_siblings, name, attrs, text,
                               **kwargs)
      findPreviousSibling = find_previous_sibling  # BS3
  
      def find_previous_siblings(self, name=None, attrs={}, text=None,
                                 limit=None, **kwargs):
          """Returns the siblings of this Tag that match the given
          criteria and appear before this Tag in the document."""
          return self._find_all(name, attrs, text, limit,
                                self.previous_siblings, **kwargs)
      findPreviousSiblings = find_previous_siblings   # BS3
      fetchPreviousSiblings = find_previous_siblings  # BS2
  
      def find_parent(self, name=None, attrs={}, **kwargs):
          """Returns the closest parent of this Tag that matches the given
          criteria."""
          # NOTE: We can't use _find_one because findParents takes a different
          # set of arguments.
          r = None
          l = self.find_parents(name, attrs, 1, **kwargs)
          if l:
              r = l[0]
          return r
      findParent = find_parent  # BS3
  
      def find_parents(self, name=None, attrs={}, limit=None, **kwargs):
          """Returns the parents of this Tag that match the given
          criteria."""
  
          return self._find_all(name, attrs, None, limit, self.parents,
                               **kwargs)
      findParents = find_parents   # BS3
      fetchParents = find_parents  # BS2
  
      @property
      def next(self):
          return self.next_element
  
      @property
      def previous(self):
          return self.previous_element
  
      #These methods do the real heavy lifting.
  
      def _find_one(self, method, name, attrs, text, **kwargs):
          r = None
          l = method(name, attrs, text, 1, **kwargs)
          if l:
              r = l[0]
          return r
  
      def _find_all(self, name, attrs, text, limit, generator, **kwargs):
          "Iterates over a generator looking for things that match."
  
          if text is None and 'string' in kwargs:
              text = kwargs['string']
              del kwargs['string']
  
          if isinstance(name, SoupStrainer):
              strainer = name
          else:
              strainer = SoupStrainer(name, attrs, text, **kwargs)
  
          if text is None and not limit and not attrs and not kwargs:
              if name is True or name is None:
                  # Optimization to find all tags.
                  result = (element for element in generator
                            if isinstance(element, Tag))
                  return ResultSet(strainer, result)
              elif isinstance(name, str):
                  # Optimization to find all tags with a given name.
                  result = (element for element in generator
                            if isinstance(element, Tag)
                              and element.name == name)
                  return ResultSet(strainer, result)
          results = ResultSet(strainer)
          while True:
              try:
                  i = next(generator)
              except StopIteration:
                  break
              if i:
                  found = strainer.search(i)
                  if found:
                      results.append(found)
                      if limit and len(results) >= limit:
                          break
          return results
  
      #These generators can be used to navigate starting from both
      #NavigableStrings and Tags.
      @property
      def next_elements(self):
          i = self.next_element
          while i is not None:
              yield i
              i = i.next_element
  
      @property
      def next_siblings(self):
          i = self.next_sibling
          while i is not None:
              yield i
              i = i.next_sibling
  
      @property
      def previous_elements(self):
          i = self.previous_element
          while i is not None:
              yield i
              i = i.previous_element
  
      @property
      def previous_siblings(self):
          i = self.previous_sibling
          while i is not None:
              yield i
              i = i.previous_sibling
  
      @property
      def parents(self):
          i = self.parent
          while i is not None:
              yield i
              i = i.parent
  
      # Methods for supporting CSS selectors.
  
      tag_name_re = re.compile('^[a-zA-Z0-9][-.a-zA-Z0-9:_]*$')
  
      # /^([a-zA-Z0-9][-.a-zA-Z0-9:_]*)\[(\w+)([=~\|\^\$\*]?)=?"?([^\]"]*)"?\]$/
      #   \---------------------------/  \---/\-------------/    \-------/
      #     |                              |         |               |
      #     |                              |         |           The value
      #     |                              |    ~,|,^,$,* or =
      #     |                           Attribute
      #    Tag
      attribselect_re = re.compile(
          r'^(?P<tag>[a-zA-Z0-9][-.a-zA-Z0-9:_]*)?\[(?P<attribute>[\w-]+)(?P<operator>[=~\|\^\$\*]?)' +
          r'=?"?(?P<value>[^\]"]*)"?\]$'
          )
  
      def _attr_value_as_string(self, value, default=None):
          """Force an attribute value into a string representation.
          A multi-valued attribute will be converted into a
          space-separated stirng.
          """
          value = self.get(value, default)
          if isinstance(value, list) or isinstance(value, tuple):
              value =" ".join(value)
          return value
  
      def _tag_name_matches_and(self, function, tag_name):
          if not tag_name:
              return function
          else:
              def _match(tag):
                  return tag.name == tag_name and function(tag)
              return _match
  
      def _attribute_checker(self, operator, attribute, value=''):
          """Create a function that performs a CSS selector operation.
          Takes an operator, attribute and optional value. Returns a
          function that will return True for elements that match that
          combination.
          """
          if operator == '=':
              # string representation of `attribute` is equal to `value`
              return lambda el: el._attr_value_as_string(attribute) == value
          elif operator == '~':
              # space-separated list representation of `attribute`
              # contains `value`
              def _includes_value(element):
                  attribute_value = element.get(attribute, [])
                  if not isinstance(attribute_value, list):
                      attribute_value = attribute_value.split()
                  return value in attribute_value
              return _includes_value
          elif operator == '^':
              # string representation of `attribute` starts with `value`
              return lambda el: el._attr_value_as_string(
                  attribute, '').startswith(value)
          elif operator == '$':
              # string representation of `attribute` ends with `value`
              return lambda el: el._attr_value_as_string(
                  attribute, '').endswith(value)
          elif operator == '*':
              # string representation of `attribute` contains `value`
              return lambda el: value in el._attr_value_as_string(attribute, '')
          elif operator == '|':
              # string representation of `attribute` is either exactly
              # `value` or starts with `value` and then a dash.
              def _is_or_starts_with_dash(element):
                  attribute_value = element._attr_value_as_string(attribute, '')
                  return (attribute_value == value or attribute_value.startswith(
                          value + '-'))
              return _is_or_starts_with_dash
          else:
              return lambda el: el.has_attr(attribute)
  
      # Old non-property versions of the generators, for backwards
      # compatibility with BS3.
      def nextGenerator(self):
          return self.next_elements
  
      def nextSiblingGenerator(self):
          return self.next_siblings
  
      def previousGenerator(self):
          return self.previous_elements
  
      def previousSiblingGenerator(self):
          return self.previous_siblings
  
      def parentGenerator(self):
          return self.parents
  
  
  class NavigableString(str, PageElement):
  
      PREFIX = ''
      SUFFIX = ''
  
      # We can't tell just by looking at a string whether it's contained
      # in an XML document or an HTML document.
  
      known_xml = None
  
      def __new__(cls, value):
          """Create a new NavigableString.
          When unpickling a NavigableString, this method is called with
          the string in DEFAULT_OUTPUT_ENCODING. That encoding needs to be
          passed in to the superclass's __new__ or the superclass won't know
          how to handle non-ASCII characters.
          """
          if isinstance(value, str):
              u = str.__new__(cls, value)
          else:
              u = str.__new__(cls, value, DEFAULT_OUTPUT_ENCODING)
          u.setup()
          return u
  
      def __copy__(self):
          """A copy of a NavigableString has the same contents and class
          as the original, but it is not connected to the parse tree.
          """
          return type(self)(self)
  
      def __getnewargs__(self):
          return (str(self),)
  
      def __getattr__(self, attr):
          """text.string gives you text. This is for backwards
          compatibility for Navigable*String, but for CData* it lets you
          get the string without the CData wrapper."""
          if attr == 'string':
              return self
          else:
              raise AttributeError(
                  "'%s' object has no attribute '%s'" % (
                      self.__class__.__name__, attr))
  
      def output_ready(self, formatter="minimal"):
          output = self.format_string(self, formatter)
          return self.PREFIX + output + self.SUFFIX
  
      @property
      def name(self):
          return None
  
      @name.setter
      def name(self, name):
          raise AttributeError("A NavigableString cannot be given a name.")
  
  class PreformattedString(NavigableString):
      """A NavigableString not subject to the normal formatting rules.
      The string will be passed into the formatter (to trigger side effects),
      but the return value will be ignored.
      """
  
      def output_ready(self, formatter="minimal"):
          """CData strings are passed into the formatter.
          But the return value is ignored."""
          self.format_string(self, formatter)
          return self.PREFIX + self + self.SUFFIX
  
  class CData(PreformattedString):
  
      PREFIX = '<![CDATA['
      SUFFIX = ']]>'
  
  class ProcessingInstruction(PreformattedString):
      """A SGML processing instruction."""
  
      PREFIX = '<?'
      SUFFIX = '>'
  
  class XMLProcessingInstruction(ProcessingInstruction):
      """An XML processing instruction."""
      PREFIX = '<?'
      SUFFIX = '?>'
  
  class Comment(PreformattedString):
  
      PREFIX = '<!--'
      SUFFIX = '-->'
  
  
  class Declaration(PreformattedString):
      PREFIX = '<?'
      SUFFIX = '?>'
  
  
  class Doctype(PreformattedString):
  
      @classmethod
      def for_name_and_ids(cls, name, pub_id, system_id):
          value = name or ''
          if pub_id is not None:
              value += ' PUBLIC "%s"' % pub_id
              if system_id is not None:
                  value += ' "%s"' % system_id
          elif system_id is not None:
              value += ' SYSTEM "%s"' % system_id
  
          return Doctype(value)
  
      PREFIX = '<!DOCTYPE '
      SUFFIX = '>\n'
  
  
  class Tag(PageElement):
  
      """Represents a found HTML tag with its attributes and contents."""
  
      def __init__(self, parser=None, builder=None, name=None, namespace=None,
                   prefix=None, attrs=None, parent=None, previous=None,
                   is_xml=None):
          "Basic constructor."
  
          if parser is None:
              self.parser_class = None
          else:
              # We don't actually store the parser object: that lets extracted
              # chunks be garbage-collected.
              self.parser_class = parser.__class__
          if name is None:
              raise ValueError("No value provided for new tag's name.")
          self.name = name
          self.namespace = namespace
          self.prefix = prefix
          if builder is not None:
              preserve_whitespace_tags = builder.preserve_whitespace_tags
          else:
              if is_xml:
                  preserve_whitespace_tags = []
              else:
                  preserve_whitespace_tags = HTMLAwareEntitySubstitution.preserve_whitespace_tags
          self.preserve_whitespace_tags = preserve_whitespace_tags
          if attrs is None:
              attrs = {}
          elif attrs:
              if builder is not None and builder.cdata_list_attributes:
                  attrs = builder._replace_cdata_list_attribute_values(
                      self.name, attrs)
              else:
                  attrs = dict(attrs)
          else:
              attrs = dict(attrs)
  
          # If possible, determine ahead of time whether this tag is an
          # XML tag.
          if builder:
              self.known_xml = builder.is_xml
          else:
              self.known_xml = is_xml
          self.attrs = attrs
          self.contents = []
          self.setup(parent, previous)
          self.hidden = False
  
          # Set up any substitutions, such as the charset in a META tag.
          if builder is not None:
              builder.set_up_substitutions(self)
              self.can_be_empty_element = builder.can_be_empty_element(name)
          else:
              self.can_be_empty_element = False
  
      parserClass = _alias("parser_class")  # BS3
  
      def __copy__(self):
          """A copy of a Tag is a new Tag, unconnected to the parse tree.
          Its contents are a copy of the old Tag's contents.
          """
          clone = type(self)(None, self.builder, self.name, self.namespace,
                             self.nsprefix, self.attrs, is_xml=self._is_xml)
          for attr in ('can_be_empty_element', 'hidden'):
              setattr(clone, attr, getattr(self, attr))
          for child in self.contents:
              clone.append(child.__copy__())
          return clone
  
      @property
      def is_empty_element(self):
          """Is this tag an empty-element tag? (aka a self-closing tag)
          A tag that has contents is never an empty-element tag.
          A tag that has no contents may or may not be an empty-element
          tag. It depends on the builder used to create the tag. If the
          builder has a designated list of empty-element tags, then only
          a tag whose name shows up in that list is considered an
          empty-element tag.
          If the builder has no designated list of empty-element tags,
          then any tag with no contents is an empty-element tag.
          """
          return len(self.contents) == 0 and self.can_be_empty_element
      isSelfClosing = is_empty_element  # BS3
  
      @property
      def string(self):
          """Convenience property to get the single string within this tag.
          :Return: If this tag has a single string child, return value
           is that string. If this tag has no children, or more than one
           child, return value is None. If this tag has one child tag,
           return value is the 'string' attribute of the child tag,
           recursively.
          """
          if len(self.contents) != 1:
              return None
          child = self.contents[0]
          if isinstance(child, NavigableString):
              return child
          return child.string
  
      @string.setter
      def string(self, string):
          self.clear()
          self.append(string.__class__(string))
  
      def _all_strings(self, strip=False, types=(NavigableString, CData)):
          """Yield all strings of certain classes, possibly stripping them.
          By default, yields only NavigableString and CData objects. So
          no comments, processing instructions, etc.
          """
          for descendant in self.descendants:
              if (
                  (types is None and not isinstance(descendant, NavigableString))
                  or
                  (types is not None and type(descendant) not in types)):
                  continue
              if strip:
                  descendant = descendant.strip()
                  if len(descendant) == 0:
                      continue
              yield descendant
  
      strings = property(_all_strings)
  
      @property
      def stripped_strings(self):
          for string in self._all_strings(True):
              yield string
  
      def get_text(self, separator="", strip=False,
                   types=(NavigableString, CData)):
          """
          Get all child strings, concatenated using the given separator.
          """
          return separator.join([s for s in self._all_strings(
                      strip, types=types)])
      getText = get_text
      text = property(get_text)
  
      def decompose(self):
          """Recursively destroys the contents of this tree."""
          self.extract()
          i = self
          while i is not None:
              next = i.next_element
              i.__dict__.clear()
              i.contents = []
              i = next
  
      def clear(self, decompose=False):
          """
          Extract all children. If decompose is True, decompose instead.
          """
          if decompose:
              for element in self.contents[:]:
                  if isinstance(element, Tag):
                      element.decompose()
                  else:
                      element.extract()
          else:
              for element in self.contents[:]:
                  element.extract()
  
      def index(self, element):
          """
          Find the index of a child by identity, not value. Avoids issues with
          tag.contents.index(element) getting the index of equal elements.
          """
          for i, child in enumerate(self.contents):
              if child is element:
                  return i
          raise ValueError("Tag.index: element not in tag")
  
      def get(self, key, default=None):
          """Returns the value of the 'key' attribute for the tag, or
          the value given for 'default' if it doesn't have that
          attribute."""
          return self.attrs.get(key, default)
  
      def has_attr(self, key):
          return key in self.attrs
  
      def __hash__(self):
          return str(self).__hash__()
  
      def __getitem__(self, key):
          """tag[key] returns the value of the 'key' attribute for the tag,
          and throws an exception if it's not there."""
          return self.attrs[key]
  
      def __iter__(self):
          "Iterating over a tag iterates over its contents."
          return iter(self.contents)
  
      def __len__(self):
          "The length of a tag is the length of its list of contents."
          return len(self.contents)
  
      def __contains__(self, x):
          return x in self.contents
  
      def __bool__(self):
          "A tag is non-None even if it has no contents."
          return True
  
      def __setitem__(self, key, value):
          """Setting tag[key] sets the value of the 'key' attribute for the
          tag."""
          self.attrs[key] = value
  
      def __delitem__(self, key):
          "Deleting tag[key] deletes all 'key' attributes for the tag."
          self.attrs.pop(key, None)
  
      def __call__(self, *args, **kwargs):
          """Calling a tag like a function is the same as calling its
          find_all() method. Eg. tag('a') returns a list of all the A tags
          found within this tag."""
          return self.find_all(*args, **kwargs)
  
      def __getattr__(self, tag):
          #print "Getattr %s.%s" % (self.__class__, tag)
          if len(tag) > 3 and tag.endswith('Tag'):
              # BS3: soup.aTag -> "soup.find("a")
              tag_name = tag[:-3]
              warnings.warn(
                  '.%sTag is deprecated, use .find("%s") instead.' % (
                      tag_name, tag_name))
              return self.find(tag_name)
          # We special case contents to avoid recursion.
          elif not tag.startswith("__") and not tag == "contents":
              return self.find(tag)
          raise AttributeError(
              "'%s' object has no attribute '%s'" % (self.__class__, tag))
  
      def __eq__(self, other):
          """Returns true iff this tag has the same name, the same attributes,
          and the same contents (recursively) as the given tag."""
          if self is other:
              return True
          if (not hasattr(other, 'name') or
              not hasattr(other, 'attrs') or
              not hasattr(other, 'contents') or
              self.name != other.name or
              self.attrs != other.attrs or
              len(self) != len(other)):
              return False
          for i, my_child in enumerate(self.contents):
              if my_child != other.contents[i]:
                  return False
          return True
  
      def __ne__(self, other):
          """Returns true iff this tag is not identical to the other tag,
          as defined in __eq__."""
          return not self == other
  
      def __repr__(self, encoding="unicode-escape"):
          """Renders this tag as a string."""
          if PY3K:
              # "The return value must be a string object", i.e. Unicode
              return self.decode()
          else:
              # "The return value must be a string object", i.e. a bytestring.
              # By convention, the return value of __repr__ should also be
              # an ASCII string.
              return self.encode(encoding)
  
      def __unicode__(self):
          return self.decode()
  
      def __str__(self):
          if PY3K:
              return self.decode()
          else:
              return self.encode()
  
      if PY3K:
          __str__ = __repr__ = __unicode__
  
      def encode(self, encoding=DEFAULT_OUTPUT_ENCODING,
                 indent_level=None, formatter="minimal",
                 errors="xmlcharrefreplace"):
          # Turn the data structure into Unicode, then encode the
          # Unicode.
          u = self.decode(indent_level, encoding, formatter)
          return u.encode(encoding, errors)
  
      def _should_pretty_print(self, indent_level):
          """Should this tag be pretty-printed?"""
  
          return (
              indent_level is not None
              and self.name not in self.preserve_whitespace_tags
          )
  
      def decode(self, indent_level=None,
                 eventual_encoding=DEFAULT_OUTPUT_ENCODING,
                 formatter="minimal"):
          """Returns a Unicode representation of this tag and its contents.
          :param eventual_encoding: The tag is destined to be
             encoded into this encoding. This method is _not_
             responsible for performing that encoding. This information
             is passed in so that it can be substituted in if the
             document contains a <META> tag that mentions the document's
             encoding.
          """
  
          # First off, turn a string formatter into a function. This
          # will stop the lookup from happening over and over again.
          if not isinstance(formatter, collections.Callable):
              formatter = self._formatter_for_name(formatter)
  
          attrs = []
          if self.attrs:
              for key, val in sorted(self.attrs.items()):
                  if val is None:
                      decoded = key
                  else:
                      if isinstance(val, list) or isinstance(val, tuple):
                          val = ' '.join(val)
                      elif not isinstance(val, str):
                          val = str(val)
                      elif (
                          isinstance(val, AttributeValueWithCharsetSubstitution)
                          and eventual_encoding is not None):
                          val = val.encode(eventual_encoding)
  
                      text = self.format_string(val, formatter)
                      decoded = (
                          str(key) + '='
                          + EntitySubstitution.quoted_attribute_value(text))
                  attrs.append(decoded)
          close = ''
          closeTag = ''
  
          prefix = ''
          if self.prefix:
              prefix = self.prefix + ":"
  
          if self.is_empty_element:
              close = '/'
          else:
              closeTag = '</%s%s>' % (prefix, self.name)
  
          pretty_print = self._should_pretty_print(indent_level)
          space = ''
          indent_space = ''
          if indent_level is not None:
              indent_space = (' ' * (indent_level - 1))
          if pretty_print:
              space = indent_space
              indent_contents = indent_level + 1
          else:
              indent_contents = None
          contents = self.decode_contents(
              indent_contents, eventual_encoding, formatter)
  
          if self.hidden:
              # This is the 'document root' object.
              s = contents
          else:
              s = []
              attribute_string = ''
              if attrs:
                  attribute_string = ' ' + ' '.join(attrs)
              if indent_level is not None:
                  # Even if this particular tag is not pretty-printed,
                  # we should indent up to the start of the tag.
                  s.append(indent_space)
              s.append('<%s%s%s%s>' % (
                      prefix, self.name, attribute_string, close))
              if pretty_print:
                  s.append("\n")
              s.append(contents)
              if pretty_print and contents and contents[-1] != "\n":
                  s.append("\n")
              if pretty_print and closeTag:
                  s.append(space)
              s.append(closeTag)
              if indent_level is not None and closeTag and self.next_sibling:
                  # Even if this particular tag is not pretty-printed,
                  # we're now done with the tag, and we should add a
                  # newline if appropriate.
                  s.append("\n")
              s = ''.join(s)
          return s
  
      def prettify(self, encoding=None, formatter="minimal"):
          if encoding is None:
              return self.decode(True, formatter=formatter)
          else:
              return self.encode(encoding, True, formatter=formatter)
  
      def decode_contents(self, indent_level=None,
                         eventual_encoding=DEFAULT_OUTPUT_ENCODING,
                         formatter="minimal"):
          """Renders the contents of this tag as a Unicode string.
          :param indent_level: Each line of the rendering will be
             indented this many spaces.
          :param eventual_encoding: The tag is destined to be
             encoded into this encoding. This method is _not_
             responsible for performing that encoding. This information
             is passed in so that it can be substituted in if the
             document contains a <META> tag that mentions the document's
             encoding.
          :param formatter: The output formatter responsible for converting
             entities to Unicode characters.
          """
          # First off, turn a string formatter into a function. This
          # will stop the lookup from happening over and over again.
          if not isinstance(formatter, collections.Callable):
              formatter = self._formatter_for_name(formatter)
  
          pretty_print = (indent_level is not None)
          s = []
          for c in self:
              text = None
              if isinstance(c, NavigableString):
                  text = c.output_ready(formatter)
              elif isinstance(c, Tag):
                  s.append(c.decode(indent_level, eventual_encoding,
                                    formatter))
              if text and indent_level and not self.name == 'pre':
                  text = text.strip()
              if text:
                  if pretty_print and not self.name == 'pre':
                      s.append(" " * (indent_level - 1))
                  s.append(text)
                  if pretty_print and not self.name == 'pre':
                      s.append("\n")
          return ''.join(s)
  
      def encode_contents(
          self, indent_level=None, encoding=DEFAULT_OUTPUT_ENCODING,
          formatter="minimal"):
          """Renders the contents of this tag as a bytestring.
          :param indent_level: Each line of the rendering will be
             indented this many spaces.
          :param eventual_encoding: The bytestring will be in this encoding.
          :param formatter: The output formatter responsible for converting
             entities to Unicode characters.
          """
  
          contents = self.decode_contents(indent_level, encoding, formatter)
          return contents.encode(encoding)
  
      # Old method for BS3 compatibility
      def renderContents(self, encoding=DEFAULT_OUTPUT_ENCODING,
                         prettyPrint=False, indentLevel=0):
          if not prettyPrint:
              indentLevel = None
          return self.encode_contents(
              indent_level=indentLevel, encoding=encoding)
  
      #Soup methods
  
      def find(self, name=None, attrs={}, recursive=True, text=None,
               **kwargs):
          """Return only the first child of this Tag matching the given
          criteria."""
          r = None
          l = self.find_all(name, attrs, recursive, text, 1, **kwargs)
          if l:
              r = l[0]
          return r
      findChild = find
  
      def find_all(self, name=None, attrs={}, recursive=True, text=None,
                   limit=None, **kwargs):
          """Extracts a list of Tag objects that match the given
          criteria.  You can specify the name of the Tag and any
          attributes you want the Tag to have.
          The value of a key-value pair in the 'attrs' map can be a
          string, a list of strings, a regular expression object, or a
          callable that takes a string and returns whether or not the
          string matches for some custom definition of 'matches'. The
          same is true of the tag name."""
  
          generator = self.descendants
          if not recursive:
              generator = self.children
          return self._find_all(name, attrs, text, limit, generator, **kwargs)
      findAll = find_all       # BS3
      findChildren = find_all  # BS2
  
      #Generator methods
      @property
      def children(self):
          # return iter() to make the purpose of the method clear
          return iter(self.contents)  # XXX This seems to be untested.
  
      @property
      def descendants(self):
          if not len(self.contents):
              return
          stopNode = self._last_descendant().next_element
          current = self.contents[0]
          while current is not stopNode:
              yield current
              current = current.next_element
  
      # CSS selector code
  
      _selector_combinators = ['>', '+', '~']
      _select_debug = False
      quoted_colon = re.compile('"[^"]*:[^"]*"')
      def select_one(self, selector):
          """Perform a CSS selection operation on the current element."""
          value = self.select(selector, limit=1)
          if value:
              return value[0]
          return None
  
      def select(self, selector, _candidate_generator=None, limit=None):
          """Perform a CSS selection operation on the current element."""
  
          # Handle grouping selectors if ',' exists, ie: p,a
          if ',' in selector:
              context = []
              for partial_selector in selector.split(','):
                  partial_selector = partial_selector.strip()
                  if partial_selector == '':
                      raise ValueError('Invalid group selection syntax: %s' % selector)
                  candidates = self.select(partial_selector, limit=limit)
                  for candidate in candidates:
                      if candidate not in context:
                          context.append(candidate)
  
                  if limit and len(context) >= limit:
                      break
              return context
          tokens = shlex.split(selector)
          current_context = [self]
  
          if tokens[-1] in self._selector_combinators:
              raise ValueError(
                  'Final combinator "%s" is missing an argument.' % tokens[-1])
  
          if self._select_debug:
              print('Running CSS selector "%s"' % selector)
  
          for index, token in enumerate(tokens):
              new_context = []
              new_context_ids = set([])
  
              if tokens[index-1] in self._selector_combinators:
                  # This token was consumed by the previous combinator. Skip it.
                  if self._select_debug:
                      print('  Token was consumed by the previous combinator.')
                  continue
  
              if self._select_debug:
                  print(' Considering token "%s"' % token)
              recursive_candidate_generator = None
              tag_name = None
  
              # Each operation corresponds to a checker function, a rule
              # for determining whether a candidate matches the
              # selector. Candidates are generated by the active
              # iterator.
              checker = None
  
              m = self.attribselect_re.match(token)
              if m is not None:
                  # Attribute selector
                  tag_name, attribute, operator, value = m.groups()
                  checker = self._attribute_checker(operator, attribute, value)
  
              elif '#' in token:
                  # ID selector
                  tag_name, tag_id = token.split('#', 1)
                  def id_matches(tag):
                      return tag.get('id', None) == tag_id
                  checker = id_matches
  
              elif '.' in token:
                  # Class selector
                  tag_name, klass = token.split('.', 1)
                  classes = set(klass.split('.'))
                  def classes_match(candidate):
                      return classes.issubset(candidate.get('class', []))
                  checker = classes_match
  
              elif ':' in token and not self.quoted_colon.search(token):
                  # Pseudo-class
                  tag_name, pseudo = token.split(':', 1)
                  if tag_name == '':
                      raise ValueError(
                          "A pseudo-class must be prefixed with a tag name.")
                  pseudo_attributes = re.match('([a-zA-Z\d-]+)\(([a-zA-Z\d]+)\)', pseudo)
                  found = []
                  if pseudo_attributes is None:
                      pseudo_type = pseudo
                      pseudo_value = None
                  else:
                      pseudo_type, pseudo_value = pseudo_attributes.groups()
                  if pseudo_type == 'nth-of-type':
                      try:
                          pseudo_value = int(pseudo_value)
                      except:
                          raise NotImplementedError(
                              'Only numeric values are currently supported for the nth-of-type pseudo-class.')
                      if pseudo_value < 1:
                          raise ValueError(
                              'nth-of-type pseudo-class value must be at least 1.')
                      class Counter(object):
                          def __init__(self, destination):
                              self.count = 0
                              self.destination = destination
  
                          def nth_child_of_type(self, tag):
                              self.count += 1
                              if self.count == self.destination:
                                  return True
                              else:
                                  return False
                      checker = Counter(pseudo_value).nth_child_of_type
                  else:
                      raise NotImplementedError(
                          'Only the following pseudo-classes are implemented: nth-of-type.')
  
              elif token == '*':
                  # Star selector -- matches everything
                  pass
              elif token == '>':
                  # Run the next token as a CSS selector against the
                  # direct children of each tag in the current context.
                  recursive_candidate_generator = lambda tag: tag.children
              elif token == '~':
                  # Run the next token as a CSS selector against the
                  # siblings of each tag in the current context.
                  recursive_candidate_generator = lambda tag: tag.next_siblings
              elif token == '+':
                  # For each tag in the current context, run the next
                  # token as a CSS selector against the tag's next
                  # sibling that's a tag.
                  def next_tag_sibling(tag):
                      yield tag.find_next_sibling(True)
                  recursive_candidate_generator = next_tag_sibling
  
              elif self.tag_name_re.match(token):
                  # Just a tag name.
                  tag_name = token
              else:
                  raise ValueError(
                      'Unsupported or invalid CSS selector: "%s"' % token)
              if recursive_candidate_generator:
                  # This happens when the selector looks like  "> foo".
                  #
                  # The generator calls select() recursively on every
                  # member of the current context, passing in a different
                  # candidate generator and a different selector.
                  #
                  # In the case of "> foo", the candidate generator is
                  # one that yields a tag's direct children (">"), and
                  # the selector is "foo".
                  next_token = tokens[index+1]
                  def recursive_select(tag):
                      if self._select_debug:
                          print('    Calling select("%s") recursively on %s %s' % (next_token, tag.name, tag.attrs))
                          print('-' * 40)
                      for i in tag.select(next_token, recursive_candidate_generator):
                          if self._select_debug:
                              print('(Recursive select picked up candidate %s %s)' % (i.name, i.attrs))
                          yield i
                      if self._select_debug:
                          print('-' * 40)
                  _use_candidate_generator = recursive_select
              elif _candidate_generator is None:
                  # By default, a tag's candidates are all of its
                  # children. If tag_name is defined, only yield tags
                  # with that name.
                  if self._select_debug:
                      if tag_name:
                          check = "[any]"
                      else:
                          check = tag_name
                      print('   Default candidate generator, tag name="%s"' % check)
                  if self._select_debug:
                      # This is redundant with later code, but it stops
                      # a bunch of bogus tags from cluttering up the
                      # debug log.
                      def default_candidate_generator(tag):
                          for child in tag.descendants:
                              if not isinstance(child, Tag):
                                  continue
                              if tag_name and not child.name == tag_name:
                                  continue
                              yield child
                      _use_candidate_generator = default_candidate_generator
                  else:
                      _use_candidate_generator = lambda tag: tag.descendants
              else:
                  _use_candidate_generator = _candidate_generator
  
              count = 0
              for tag in current_context:
                  if self._select_debug:
                      print("    Running candidate generator on %s %s" % (
                          tag.name, repr(tag.attrs)))
                  for candidate in _use_candidate_generator(tag):
                      if not isinstance(candidate, Tag):
                          continue
                      if tag_name and candidate.name != tag_name:
                          continue
                      if checker is not None:
                          try:
                              result = checker(candidate)
                          except StopIteration:
                              # The checker has decided we should no longer
                              # run the generator.
                              break
                      if checker is None or result:
                          if self._select_debug:
                              print("     SUCCESS %s %s" % (candidate.name, repr(candidate.attrs)))
                          if id(candidate) not in new_context_ids:
                              # If a tag matches a selector more than once,
                              # don't include it in the context more than once.
                              new_context.append(candidate)
                              new_context_ids.add(id(candidate))
                      elif self._select_debug:
                          print("     FAILURE %s %s" % (candidate.name, repr(candidate.attrs)))
  
              current_context = new_context
          if limit and len(current_context) >= limit:
              current_context = current_context[:limit]
  
          if self._select_debug:
              print("Final verdict:")
              for i in current_context:
                  print(" %s %s" % (i.name, i.attrs))
          return current_context
  
      # Old names for backwards compatibility
      def childGenerator(self):
          return self.children
  
      def recursiveChildGenerator(self):
          return self.descendants
  
      def has_key(self, key):
          """This was kind of misleading because has_key() (attributes)
          was different from __in__ (contents). has_key() is gone in
          Python 3, anyway."""
          warnings.warn('has_key is deprecated. Use has_attr("%s") instead.' % (
                  key))
          return self.has_attr(key)
  
  # Next, a couple classes to represent queries and their results.
  class SoupStrainer(object):
      """Encapsulates a number of ways of matching a markup element (tag or
      text)."""
  
      def __init__(self, name=None, attrs={}, text=None, **kwargs):
          self.name = self._normalize_search_value(name)
          if not isinstance(attrs, dict):
              # Treat a non-dict value for attrs as a search for the 'class'
              # attribute.
              kwargs['class'] = attrs
              attrs = None
  
          if 'class_' in kwargs:
              # Treat class_="foo" as a search for the 'class'
              # attribute, overriding any non-dict value for attrs.
              kwargs['class'] = kwargs['class_']
              del kwargs['class_']
  
          if kwargs:
              if attrs:
                  attrs = attrs.copy()
                  attrs.update(kwargs)
              else:
                  attrs = kwargs
          normalized_attrs = {}
          for key, value in list(attrs.items()):
              normalized_attrs[key] = self._normalize_search_value(value)
  
          self.attrs = normalized_attrs
          self.text = self._normalize_search_value(text)
  
      def _normalize_search_value(self, value):
          # Leave it alone if it's a Unicode string, a callable, a
          # regular expression, a boolean, or None.
          if (isinstance(value, str) or isinstance(value, collections.Callable) or hasattr(value, 'match')
              or isinstance(value, bool) or value is None):
              return value
  
          # If it's a bytestring, convert it to Unicode, treating it as UTF-8.
          if isinstance(value, bytes):
              return value.decode("utf8")
  
          # If it's listlike, convert it into a list of strings.
          if hasattr(value, '__iter__'):
              new_value = []
              for v in value:
                  if (hasattr(v, '__iter__') and not isinstance(v, bytes)
                      and not isinstance(v, str)):
                      # This is almost certainly the user's mistake. In the
                      # interests of avoiding infinite loops, we'll let
                      # it through as-is rather than doing a recursive call.
                      new_value.append(v)
                  else:
                      new_value.append(self._normalize_search_value(v))
              return new_value
  
          # Otherwise, convert it into a Unicode string.
          # The unicode(str()) thing is so this will do the same thing on Python 2
          # and Python 3.
          return str(str(value))
  
      def __str__(self):
          if self.text:
              return self.text
          else:
              return "%s|%s" % (self.name, self.attrs)
  
      def search_tag(self, markup_name=None, markup_attrs={}):
          found = None
          markup = None
          if isinstance(markup_name, Tag):
              markup = markup_name
              markup_attrs = markup
          call_function_with_tag_data = (
              isinstance(self.name, collections.Callable)
              and not isinstance(markup_name, Tag))
  
          if ((not self.name)
              or call_function_with_tag_data
              or (markup and self._matches(markup, self.name))
              or (not markup and self._matches(markup_name, self.name))):
              if call_function_with_tag_data:
                  match = self.name(markup_name, markup_attrs)
              else:
                  match = True
                  markup_attr_map = None
                  for attr, match_against in list(self.attrs.items()):
                      if not markup_attr_map:
                          if hasattr(markup_attrs, 'get'):
                              markup_attr_map = markup_attrs
                          else:
                              markup_attr_map = {}
                              for k, v in markup_attrs:
                                  markup_attr_map[k] = v
                      attr_value = markup_attr_map.get(attr)
                      if not self._matches(attr_value, match_against):
                          match = False
                          break
              if match:
                  if markup:
                      found = markup
                  else:
                      found = markup_name
          if found and self.text and not self._matches(found.string, self.text):
              found = None
          return found
      searchTag = search_tag
  
      def search(self, markup):
          # print 'looking for %s in %s' % (self, markup)
          found = None
          # If given a list of items, scan it for a text element that
          # matches.
          if hasattr(markup, '__iter__') and not isinstance(markup, (Tag, str)):
              for element in markup:
                  if isinstance(element, NavigableString) \
                         and self.search(element):
                      found = element
                      break
          # If it's a Tag, make sure its name or attributes match.
          # Don't bother with Tags if we're searching for text.
          elif isinstance(markup, Tag):
              if not self.text or self.name or self.attrs:
                  found = self.search_tag(markup)
          # If it's text, make sure the text matches.
          elif isinstance(markup, NavigableString) or \
                   isinstance(markup, str):
              if not self.name and not self.attrs and self._matches(markup, self.text):
                  found = markup
          else:
              raise Exception(
                  "I don't know how to match against a %s" % markup.__class__)
          return found
  
      def _matches(self, markup, match_against):
          # print u"Matching %s against %s" % (markup, match_against)
          result = False
          if isinstance(markup, list) or isinstance(markup, tuple):
              # This should only happen when searching a multi-valued attribute
              # like 'class'.
              for item in markup:
                  if self._matches(item, match_against):
                      return True
              # We didn't match any particular value of the multivalue
              # attribute, but maybe we match the attribute value when
              # considered as a string.
              if self._matches(' '.join(markup), match_against):
                  return True
              return False
  
          if match_against is True:
              # True matches any non-None value.
              return markup is not None
  
          if isinstance(match_against, collections.Callable):
              return match_against(markup)
  
          # Custom callables take the tag as an argument, but all
          # other ways of matching match the tag name as a string.
          if isinstance(markup, Tag):
              markup = markup.name
  
          # Ensure that `markup` is either a Unicode string, or None.
          markup = self._normalize_search_value(markup)
  
          if markup is None:
              # None matches None, False, an empty string, an empty list, and so on.
              return not match_against
  
          if isinstance(match_against, str):
              # Exact string match
              return markup == match_against
  
          if hasattr(match_against, 'match'):
              # Regexp match
              return match_against.search(markup)
  
          if hasattr(match_against, '__iter__'):
              # The markup must be an exact match against something
              # in the iterable.
              return markup in match_against
  
  
  class ResultSet(list):
      """A ResultSet is just a list that keeps track of the SoupStrainer
      that created it."""
      def __init__(self, source, result=()):
          super(ResultSet, self).__init__(result)
          self.source = source
  