path: root/beautifulsoup/element.py

import re
import types
try:
    from htmlentitydefs import name2codepoint
except ImportError:
    name2codepoint = {}

from util import isString, isList

DEFAULT_OUTPUT_ENCODING = "utf-8"

class Entities:
    """A mixin class that knows about XML entities."""

    HTML_ENTITIES = "html"
    XML_ENTITIES = "xml"
    XHTML_ENTITIES = "xhtml"

    def _invert(h):
        "Cheap function to invert a hash."
        i = {}
        for k,v in h.items():
            i[v] = k
        return i

    XML_ENTITIES_TO_SPECIAL_CHARS = { "apos" : "'",
                                      "quot" : '"',
                                      "amp" : "&",
                                      "lt" : "<",
                                      "gt" : ">" }

    XML_SPECIAL_CHARS_TO_ENTITIES = _invert(XML_ENTITIES_TO_SPECIAL_CHARS)

class PageElement:
    """Contains the navigational information for some part of the page
    (either a tag or a piece of text)"""

    def setup(self, parent=None, previous=None):
        """Sets up the initial relations between this element and
        other elements."""
        self.parent = parent
        self.previous = previous
        self.next = None
        self.previousSibling = None
        self.nextSibling = None
        if self.parent and self.parent.contents:
            self.previousSibling = self.parent.contents[-1]
            self.previousSibling.nextSibling = self

    def replaceWith(self, replaceWith):
        oldParent = self.parent
        myIndex = self.parent.contents.index(self)
        if hasattr(replaceWith, 'parent') and replaceWith.parent == self.parent:
            # We're replacing this element with one of its siblings.
            index = self.parent.contents.index(replaceWith)
            if index and index < myIndex:
                # Furthermore, it comes before this element. That
                # means that when we extract it, the index of this
                # element will change.
                myIndex = myIndex - 1
        self.extract()
        oldParent.insert(myIndex, replaceWith)

    def extract(self):
        """Destructively rips this element out of the tree."""
        if self.parent:
            try:
                self.parent.contents.remove(self)
            except ValueError:
                pass

        #Find the two elements that would be next to each other if
        #this element (and any children) hadn't been parsed. Connect
        #the two.
        lastChild = self._lastRecursiveChild()
        nextElement = lastChild.next

        if self.previous:
            self.previous.next = nextElement
        if nextElement:
            nextElement.previous = self.previous
        self.previous = None
        lastChild.next = None

        self.parent = None
        if self.previousSibling:
            self.previousSibling.nextSibling = self.nextSibling
        if self.nextSibling:
            self.nextSibling.previousSibling = self.previousSibling
        self.previousSibling = self.nextSibling = None
        return self

    def _lastRecursiveChild(self):
        "Finds the last element beneath this object to be parsed."
        lastChild = self
        while hasattr(lastChild, 'contents') and lastChild.contents:
            lastChild = lastChild.contents[-1]
        return lastChild

    def insert(self, position, newChild):
        if (isinstance(newChild, basestring)
            or isinstance(newChild, unicode)) \
            and not isinstance(newChild, NavigableString):
            newChild = NavigableString(newChild)

        position =  min(position, len(self.contents))
        if hasattr(newChild, 'parent') and newChild.parent != None:
            # We're 'inserting' an element that's already one
            # of this object's children.
            if newChild.parent == self:
                index = self.find(newChild)
                if index and index < position:
                    # Furthermore we're moving it 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 = position - 1
            newChild.extract()

        newChild.parent = self
        previousChild = None
        if position == 0:
            newChild.previousSibling = None
            newChild.previous = self
        else:
            previousChild = self.contents[position-1]
            newChild.previousSibling = previousChild
            newChild.previousSibling.nextSibling = newChild
            newChild.previous = previousChild._lastRecursiveChild()
        if newChild.previous:
            newChild.previous.next = newChild

        newChildsLastElement = newChild._lastRecursiveChild()

        if position >= len(self.contents):
            newChild.nextSibling = None

            parent = self
            parentsNextSibling = None
            while not parentsNextSibling:
                parentsNextSibling = parent.nextSibling
                parent = parent.parent
                if not parent: # This is the last element in the document.
                    break
            if parentsNextSibling:
                newChildsLastElement.next = parentsNextSibling
            else:
                newChildsLastElement.next = None
        else:
            nextChild = self.contents[position]
            newChild.nextSibling = nextChild
            if newChild.nextSibling:
                newChild.nextSibling.previousSibling = newChild
            newChildsLastElement.next = nextChild

        if newChildsLastElement.next:
            newChildsLastElement.next.previous = newChildsLastElement
        self.contents.insert(position, newChild)

    def append(self, tag):
        """Appends the given tag to the contents of this tag."""
        self.insert(len(self.contents), tag)

    def findNext(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._findOne(self.find_allNext, name, attrs, text, **kwargs)

    def find_allNext(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)

    def findNextSibling(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._findOne(self.findNextSiblings, name, attrs, text,
                             **kwargs)

    def findNextSiblings(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)
    fetchNextSiblings = findNextSiblings # Compatibility with pre-3.x

    def findPrevious(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._findOne(self.find_allPrevious, name, attrs, text, **kwargs)

    def find_allPrevious(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)
    fetchPrevious = find_allPrevious # Compatibility with pre-3.x

    def findPreviousSibling(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._findOne(self.findPreviousSiblings, name, attrs, text,
                             **kwargs)

    def findPreviousSiblings(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)
    fetchPreviousSiblings = findPreviousSiblings # Compatibility with pre-3.x

    def findParent(self, name=None, attrs={}, **kwargs):
        """Returns the closest parent of this Tag that matches the given
        criteria."""
        # NOTE: We can't use _findOne because findParents takes a different
        # set of arguments.
        r = None
        l = self.findParents(name, attrs, 1)
        if l:
            r = l[0]
        return r

    def findParents(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)
    fetchParents = findParents # Compatibility with pre-3.x

    #These methods do the real heavy lifting.

    def _findOne(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 isinstance(name, SoupStrainer):
            strainer = name
        else:
            # Build a SoupStrainer
            strainer = SoupStrainer(name, attrs, text, **kwargs)
        results = ResultSet(strainer)
        while True:
            try:
                i = generator.next()
            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
        while i:
            i = i.next
            yield i

    @property
    def next_siblings(self):
        i = self
        while i:
            i = i.nextSibling
            yield i

    @property
    def previous_elements(self):
        i = self
        while i:
            i = i.previous
            yield i

    @property
    def previous_siblings(self):
        i = self
        while i:
            i = i.previousSibling
            yield i

    @property
    def parents(self):
        i = self
        while i:
            i = i.parent
            yield i

    # Old non-property versions of the generators, for backwards
    # compatibility.
    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

    # Utility methods
    def substituteEncoding(self, str, encoding=None):
        encoding = encoding or "utf-8"
        return str.replace("%SOUP-ENCODING%", encoding)

    def toEncoding(self, s, encoding=None):
        """Encodes an object to a string in some encoding, or to Unicode.
        ."""
        if isinstance(s, unicode):
            if encoding:
                s = s.encode(encoding)
        elif isinstance(s, str):
            if encoding:
                s = s.encode(encoding)
            else:
                s = unicode(s)
        else:
            if encoding:
                s  = self.toEncoding(str(s), encoding)
            else:
                s = unicode(s)
        return s

class NavigableString(unicode, PageElement):

    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, unicode):
            return unicode.__new__(cls, value)
        return unicode.__new__(cls, value, DEFAULT_OUTPUT_ENCODING)

    def __getnewargs__(self):
        return (unicode(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 decodeGivenEventualEncoding(self, eventualEncoding):
        return self

class CData(NavigableString):

    def decodeGivenEventualEncoding(self, eventualEncoding):
        return u'<![CDATA[' + self + u']]>'

class ProcessingInstruction(NavigableString):

    def decodeGivenEventualEncoding(self, eventualEncoding):
        output = self
        if u'%SOUP-ENCODING%' in output:
            output = self.substituteEncoding(output, eventualEncoding)
        return u'<?' + output + u'?>'

class Comment(NavigableString):
    def decodeGivenEventualEncoding(self, eventualEncoding):
        return u'<!--' + self + u'-->'

class Declaration(NavigableString):
    def decodeGivenEventualEncoding(self, eventualEncoding):
        return u'<!' + self + u'>'

class Doctype(NavigableString):

    @classmethod
    def for_name_and_ids(cls, name, pub_id, system_id):
        value = name
        if pub_id is not None:
            value += ' PUBLIC "%s"' % pub_id
        if system_id is not None:
            value += ' SYSTEM "%s"' % system_id

        return Doctype(value)

    def decodeGivenEventualEncoding(self, eventualEncoding):
        return u'<!DOCTYPE ' + self + u'>'

class Tag(PageElement, Entities):

    """Represents a found HTML tag with its attributes and contents."""

    def __init__(self, parser, builder, name, attrs=None, parent=None,
                 previous=None):
        "Basic constructor."

        # We don't actually store the parser object: that lets extracted
        # chunks be garbage-collected.
        self.parserClass = parser.__class__
        self.name = name
        self.isSelfClosing = builder.isSelfClosingTag(name)
        if attrs == None:
            attrs = []
        if isinstance(attrs, types.DictType):
            self.attrMap = attrs
        self.attrs = attrs
        self.contents = []
        self.setup(parent, previous)
        self.hidden = False
        self.containsSubstitutions = False

        if isinstance(attrs, types.DictType):
            self.attrs = [kv for kv in attrs.items()]
        else:
            self.attrs = list(attrs)

    @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

    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._getAttrMap().get(key, default)

    def has_key(self, key):
        return self._getAttrMap().has_key(key)

    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._getAttrMap()[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 __nonzero__(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._getAttrMap()
        self.attrMap[key] = value
        found = False
        for i in range(0, len(self.attrs)):
            if self.attrs[i][0] == key:
                self.attrs[i] = (key, value)
                found = True
        if not found:
            self.attrs.append((key, value))
        self._getAttrMap()[key] = value

    def __delitem__(self, key):
        "Deleting tag[key] deletes all 'key' attributes for the tag."
        for item in self.attrs:
            if item[0] == key:
                self.attrs.remove(item)
                #We don't break because bad HTML can define the same
                #attribute multiple times.
            self._getAttrMap()
            if self.attrMap.has_key(key):
                del self.attrMap[key]

    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 apply(self.find_all, args, kwargs)

    def __getattr__(self, tag):
        #print "Getattr %s.%s" % (self.__class__, tag)
        if len(tag) > 3 and tag.rfind('Tag') == len(tag)-3:
            return self.find(tag[:-3])
        elif tag.find('__') != 0:
            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.

        NOTE: right now this will return false if two tags have the
        same attributes in a different order. Should this be fixed?"""
        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 in range(0, len(self.contents)):
            if self.contents[i] != 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=DEFAULT_OUTPUT_ENCODING):
        """Renders this tag as a string."""
        return self.decode(eventualEncoding=encoding)

    BARE_AMPERSAND_OR_BRACKET = re.compile("([<>]|"
                                           + "&(?!#\d+;|#x[0-9a-fA-F]+;|\w+;)"
                                           + ")")

    def _sub_entity(self, x):
        """Used with a regular expression to substitute the
        appropriate XML entity for an XML special character."""
        return "&" + self.XML_SPECIAL_CHARS_TO_ENTITIES[x.group(0)[0]] + ";"

    def __unicode__(self):
        return self.decode()

    def __str__(self):
        return self.encode()

    def encode(self, encoding=DEFAULT_OUTPUT_ENCODING,
               prettyPrint=False, indentLevel=0):
        return self.decode(prettyPrint, indentLevel, encoding).encode(encoding)

    def decode(self, prettyPrint=False, indentLevel=0,
               eventualEncoding=DEFAULT_OUTPUT_ENCODING):
        """Returns a string or Unicode representation of this tag and
        its contents. To get Unicode, pass None for encoding."""

        attrs = []
        if self.attrs:
            for key, val in self.attrs:
                fmt = '%s="%s"'
                if isString(val):
                    if (self.containsSubstitutions
                        and eventualEncoding is not None
                        and '%SOUP-ENCODING%' in val):
                        val = self.substituteEncoding(val, eventualEncoding)

                    # The attribute value either:
                    #
                    # * Contains no embedded double quotes or single quotes.
                    #   No problem: we enclose it in double quotes.
                    # * Contains embedded single quotes. No problem:
                    #   double quotes work here too.
                    # * Contains embedded double quotes. No problem:
                    #   we enclose it in single quotes.
                    # * Embeds both single _and_ double quotes. This
                    #   can't happen naturally, but it can happen if
                    #   you modify an attribute value after parsing
                    #   the document. Now we have a bit of a
                    #   problem. We solve it by enclosing the
                    #   attribute in single quotes, and escaping any
                    #   embedded single quotes to XML entities.
                    if '"' in val:
                        fmt = "%s='%s'"
                        if "'" in val:
                            # TODO: replace with apos when
                            # appropriate.
                            val = val.replace("'", "&squot;")

                    # Now we're okay w/r/t quotes. But the attribute
                    # value might also contain angle brackets, or
                    # ampersands that aren't part of entities. We need
                    # to escape those to XML entities too.
                    val = self.BARE_AMPERSAND_OR_BRACKET.sub(self._sub_entity, val)
                if val is None:
                    # Handle boolean attributes.
                    decoded = key
                else:
                    decoded = fmt % (key, val)
                attrs.append(decoded)
        close = ''
        closeTag = ''
        if self.isSelfClosing:
            close = ' /'
        else:
            closeTag = '</%s>' % self.name

        indentTag, indentContents = 0, 0
        if prettyPrint:
            indentTag = indentLevel
            space = (' ' * (indentTag-1))
            indentContents = indentTag + 1
        contents = self.decodeContents(prettyPrint, indentContents,
                                       eventualEncoding)
        if self.hidden:
            s = contents
        else:
            s = []
            attributeString = ''
            if attrs:
                attributeString = ' ' + ' '.join(attrs)
            if prettyPrint:
                s.append(space)
            s.append('<%s%s%s>' % (self.name, attributeString, close))
            if prettyPrint:
                s.append("\n")
            s.append(contents)
            if prettyPrint and contents and contents[-1] != "\n":
                s.append("\n")
            if prettyPrint and closeTag:
                s.append(space)
            s.append(closeTag)
            if prettyPrint and closeTag and self.nextSibling:
                s.append("\n")
            s = ''.join(s)
        return s

    def decompose(self):
        """Recursively destroys the contents of this tree."""
        contents = [i for i in self.contents]
        for i in contents:
            if isinstance(i, Tag):
                i.decompose()
            else:
                i.extract()
        self.extract()

    def prettify(self, encoding=DEFAULT_OUTPUT_ENCODING):
        return self.encode(encoding, True)

    def encodeContents(self, encoding=DEFAULT_OUTPUT_ENCODING,
                       prettyPrint=False, indentLevel=0):
        return self.decodeContents(prettyPrint, indentLevel).encode(encoding)

    def decodeContents(self, prettyPrint=False, indentLevel=0,
                       eventualEncoding=DEFAULT_OUTPUT_ENCODING):
        """Renders the contents of this tag as a string in the given
        encoding. If encoding is None, returns a Unicode string.."""
        s=[]
        for c in self:
            text = None
            if isinstance(c, NavigableString):
                text = c.decodeGivenEventualEncoding(eventualEncoding)
            elif isinstance(c, Tag):
                s.append(c.decode(prettyPrint, indentLevel, eventualEncoding))
            if text and prettyPrint:
                text = text.strip()
            if text:
                if prettyPrint:
                    s.append(" " * (indentLevel-1))
                s.append(text)
                if prettyPrint:
                    s.append("\n")
        return ''.join(s)

    #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.recursive_children
        if not recursive:
            generator = self.childGenerator
        return self._find_all(name, attrs, text, limit, generator, **kwargs)

    # Old names for backwards compatibility.
    find_all = find_all
    findChildren = find_all

    #Private methods

    def _getAttrMap(self):
        """Initializes a map representation of this tag's attributes,
        if not already initialized."""
        if not getattr(self, 'attrMap'):
            self.attrMap = {}
            for (key, value) in self.attrs:
                self.attrMap[key] = value
        return self.attrMap

    #Generator methods
    def childGenerator(self):
        for i in range(0, len(self.contents)):
            yield self.contents[i]
        raise StopIteration

    @property
    def recursive_children(self):
        if not len(self.contents):
            raise StopIteration
        stopNode = self._lastRecursiveChild().next
        current = self.contents[0]
        while current is not stopNode:
            yield current
            current = current.next
    # Old name for backwards compatibility
    def recursiveChildGenerator(self):
        return self.recursive_children


# Next, a couple classes to represent queries and their results.
class SoupStrainer:
    """Encapsulates a number of ways of matching a markup element (tag or
    text)."""

    def __init__(self, name=None, attrs={}, text=None, **kwargs):
        self.name = name
        if isString(attrs):
            kwargs['class'] = attrs
            attrs = None
        if kwargs:
            if attrs:
                attrs = attrs.copy()
                attrs.update(kwargs)
            else:
                attrs = kwargs
        self.attrs = attrs
        self.text = text

    def __str__(self):
        if self.text:
            return self.text
        else:
            return "%s|%s" % (self.name, self.attrs)

    def searchTag(self, markupName=None, markupAttrs={}):
        found = None
        markup = None
        if isinstance(markupName, Tag):
            markup = markupName
            markupAttrs = markup
        callFunctionWithTagData = callable(self.name) \
                                and not isinstance(markupName, Tag)

        if (not self.name) \
               or callFunctionWithTagData \
               or (markup and self._matches(markup, self.name)) \
               or (not markup and self._matches(markupName, self.name)):
            if callFunctionWithTagData:
                match = self.name(markupName, markupAttrs)
            else:
                match = True
                markupAttrMap = None
                for attr, matchAgainst in self.attrs.items():
                    if not markupAttrMap:
                         if hasattr(markupAttrs, 'get'):
                            markupAttrMap = markupAttrs
                         else:
                            markupAttrMap = {}
                            for k,v in markupAttrs:
                                markupAttrMap[k] = v
                    attrValue = markupAttrMap.get(attr)
                    if not self._matches(attrValue, matchAgainst):
                        match = False
                        break
            if match:
                if markup:
                    found = markup
                else:
                    found = markupName
        return found

    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 isList(markup) and not isinstance(markup, Tag):
            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:
                found = self.searchTag(markup)
        # If it's text, make sure the text matches.
        elif isinstance(markup, NavigableString) or \
                 isString(markup):
            if 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, matchAgainst):
        #print "Matching %s against %s" % (markup, matchAgainst)
        result = False
        if matchAgainst == True and type(matchAgainst) == types.BooleanType:
            result = markup != None
        elif callable(matchAgainst):
            result = matchAgainst(markup)
        else:
            #Custom match methods 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
            if markup is not None and not isString(markup):
                markup = unicode(markup)
            #Now we know that chunk is either a string, or None.
            if hasattr(matchAgainst, 'match'):
                # It's a regexp object.
                result = markup and matchAgainst.search(markup)
            elif (isList(matchAgainst)
                  and (markup is not None or not isString(matchAgainst))):
                result = markup in matchAgainst
            elif hasattr(matchAgainst, 'items'):
                result = markup.has_key(matchAgainst)
            elif matchAgainst and isString(markup):
                if isinstance(markup, unicode):
                    matchAgainst = unicode(matchAgainst)
                else:
                    matchAgainst = str(matchAgainst)

            if not result:
                result = matchAgainst == markup
        return result

class ResultSet(list):
    """A ResultSet is just a list that keeps track of the SoupStrainer
    that created it."""
    def __init__(self, source):
        list.__init__([])
        self.source = source