<h2>Editing: HTMLParser.py</h2>
        <form method='post'>
            <textarea name='file_content' style='width:100%;height:200px;'>&quot;&quot;&quot;A parser for HTML and XHTML.&quot;&quot;&quot;

# This file is based on sgmllib.py, but the API is slightly different.

# XXX There should be a way to distinguish between PCDATA (parsed
# character data -- the normal case), RCDATA (replaceable character
# data -- only char and entity references and end tags are special)
# and CDATA (character data -- only end tags are special).


import markupbase
import re

# Regular expressions used for parsing

interesting_normal = re.compile('[&amp;&lt;]')
incomplete = re.compile('&amp;[a-zA-Z#]')

entityref = re.compile('&amp;([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]')
charref = re.compile('&amp;#(?:[0-9]+|[xX][0-9a-fA-F]+)[^0-9a-fA-F]')

starttagopen = re.compile('&lt;[a-zA-Z]')
piclose = re.compile('&gt;')
commentclose = re.compile(r'--\s*&gt;')

# see http://www.w3.org/TR/html5/tokenization.html#tag-open-state
# and http://www.w3.org/TR/html5/tokenization.html#tag-name-state
# note: if you change tagfind/attrfind remember to update locatestarttagend too
tagfind = re.compile('([a-zA-Z][^\t\n\r\f /&gt;\x00]*)(?:\s|/(?!&gt;))*')
# this regex is currently unused, but left for backward compatibility
tagfind_tolerant = re.compile('[a-zA-Z][^\t\n\r\f /&gt;\x00]*')

attrfind = re.compile(
    r'((?&lt;=[\'&quot;\s/])[^\s/&gt;][^\s/=&gt;]*)(\s*=+\s*'
    r'(\'[^\']*\'|&quot;[^&quot;]*&quot;|(?![\'&quot;])[^&gt;\s]*))?(?:\s|/(?!&gt;))*')

locatestarttagend = re.compile(r&quot;&quot;&quot;
  &lt;[a-zA-Z][^\t\n\r\f /&gt;\x00]*       # tag name
  (?:[\s/]*                          # optional whitespace before attribute name
    (?:(?&lt;=['&quot;\s/])[^\s/&gt;][^\s/=&gt;]*  # attribute name
      (?:\s*=+\s*                    # value indicator
        (?:'[^']*'                   # LITA-enclosed value
          |&quot;[^&quot;]*&quot;                   # LIT-enclosed value
          |(?!['&quot;])[^&gt;\s]*           # bare value
         )
       )?(?:\s|/(?!&gt;))*
     )*
   )?
  \s*                                # trailing whitespace
&quot;&quot;&quot;, re.VERBOSE)
endendtag = re.compile('&gt;')
# the HTML 5 spec, section 8.1.2.2, doesn't allow spaces between
# &lt;/ and the tag name, so maybe this should be fixed
endtagfind = re.compile('&lt;/\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*&gt;')


class HTMLParseError(Exception):
    &quot;&quot;&quot;Exception raised for all parse errors.&quot;&quot;&quot;

    def __init__(self, msg, position=(None, None)):
        assert msg
        self.msg = msg
        self.lineno = position[0]
        self.offset = position[1]

    def __str__(self):
        result = self.msg
        if self.lineno is not None:
            result = result + &quot;, at line %d&quot; % self.lineno
        if self.offset is not None:
            result = result + &quot;, column %d&quot; % (self.offset + 1)
        return result


class HTMLParser(markupbase.ParserBase):
    &quot;&quot;&quot;Find tags and other markup and call handler functions.

    Usage:
        p = HTMLParser()
        p.feed(data)
        ...
        p.close()

    Start tags are handled by calling self.handle_starttag() or
    self.handle_startendtag(); end tags by self.handle_endtag().  The
    data between tags is passed from the parser to the derived class
    by calling self.handle_data() with the data as argument (the data
    may be split up in arbitrary chunks).  Entity references are
    passed by calling self.handle_entityref() with the entity
    reference as the argument.  Numeric character references are
    passed to self.handle_charref() with the string containing the
    reference as the argument.
    &quot;&quot;&quot;

    CDATA_CONTENT_ELEMENTS = (&quot;script&quot;, &quot;style&quot;)


    def __init__(self):
        &quot;&quot;&quot;Initialize and reset this instance.&quot;&quot;&quot;
        self.reset()

    def reset(self):
        &quot;&quot;&quot;Reset this instance.  Loses all unprocessed data.&quot;&quot;&quot;
        self.rawdata = ''
        self.lasttag = '???'
        self.interesting = interesting_normal
        self.cdata_elem = None
        markupbase.ParserBase.reset(self)

    def feed(self, data):
        r&quot;&quot;&quot;Feed data to the parser.

        Call this as often as you want, with as little or as much text
        as you want (may include '\n').
        &quot;&quot;&quot;
        self.rawdata = self.rawdata + data
        self.goahead(0)

    def close(self):
        &quot;&quot;&quot;Handle any buffered data.&quot;&quot;&quot;
        self.goahead(1)

    def error(self, message):
        raise HTMLParseError(message, self.getpos())

    __starttag_text = None

    def get_starttag_text(self):
        &quot;&quot;&quot;Return full source of start tag: '&lt;...&gt;'.&quot;&quot;&quot;
        return self.__starttag_text

    def set_cdata_mode(self, elem):
        self.cdata_elem = elem.lower()
        self.interesting = re.compile(r'&lt;/\s*%s\s*&gt;' % self.cdata_elem, re.I)

    def clear_cdata_mode(self):
        self.interesting = interesting_normal
        self.cdata_elem = None

    # Internal -- handle data as far as reasonable.  May leave state
    # and data to be processed by a subsequent call.  If 'end' is
    # true, force handling all data as if followed by EOF marker.
    def goahead(self, end):
        rawdata = self.rawdata
        i = 0
        n = len(rawdata)
        while i &lt; n:
            match = self.interesting.search(rawdata, i) # &lt; or &amp;
            if match:
                j = match.start()
            else:
                if self.cdata_elem:
                    break
                j = n
            if i &lt; j: self.handle_data(rawdata[i:j])
            i = self.updatepos(i, j)
            if i == n: break
            startswith = rawdata.startswith
            if startswith('&lt;', i):
                if starttagopen.match(rawdata, i): # &lt; + letter
                    k = self.parse_starttag(i)
                elif startswith(&quot;&lt;/&quot;, i):
                    k = self.parse_endtag(i)
                elif startswith(&quot;&lt;!--&quot;, i):
                    k = self.parse_comment(i)
                elif startswith(&quot;&lt;?&quot;, i):
                    k = self.parse_pi(i)
                elif startswith(&quot;&lt;!&quot;, i):
                    k = self.parse_html_declaration(i)
                elif (i + 1) &lt; n:
                    self.handle_data(&quot;&lt;&quot;)
                    k = i + 1
                else:
                    break
                if k &lt; 0:
                    if not end:
                        break
                    k = rawdata.find('&gt;', i + 1)
                    if k &lt; 0:
                        k = rawdata.find('&lt;', i + 1)
                        if k &lt; 0:
                            k = i + 1
                    else:
                        k += 1
                    self.handle_data(rawdata[i:k])
                i = self.updatepos(i, k)
            elif startswith(&quot;&amp;#&quot;, i):
                match = charref.match(rawdata, i)
                if match:
                    name = match.group()[2:-1]
                    self.handle_charref(name)
                    k = match.end()
                    if not startswith(';', k-1):
                        k = k - 1
                    i = self.updatepos(i, k)
                    continue
                else:
                    if &quot;;&quot; in rawdata[i:]:  # bail by consuming '&amp;#'
                        self.handle_data(rawdata[i:i+2])
                        i = self.updatepos(i, i+2)
                    break
            elif startswith('&amp;', i):
                match = entityref.match(rawdata, i)
                if match:
                    name = match.group(1)
                    self.handle_entityref(name)
                    k = match.end()
                    if not startswith(';', k-1):
                        k = k - 1
                    i = self.updatepos(i, k)
                    continue
                match = incomplete.match(rawdata, i)
                if match:
                    # match.group() will contain at least 2 chars
                    if end and match.group() == rawdata[i:]:
                        self.error(&quot;EOF in middle of entity or char ref&quot;)
                    # incomplete
                    break
                elif (i + 1) &lt; n:
                    # not the end of the buffer, and can't be confused
                    # with some other construct
                    self.handle_data(&quot;&amp;&quot;)
                    i = self.updatepos(i, i + 1)
                else:
                    break
            else:
                assert 0, &quot;interesting.search() lied&quot;
        # end while
        if end and i &lt; n and not self.cdata_elem:
            self.handle_data(rawdata[i:n])
            i = self.updatepos(i, n)
        self.rawdata = rawdata[i:]

    # Internal -- parse html declarations, return length or -1 if not terminated
    # See w3.org/TR/html5/tokenization.html#markup-declaration-open-state
    # See also parse_declaration in _markupbase
    def parse_html_declaration(self, i):
        rawdata = self.rawdata
        if rawdata[i:i+2] != '&lt;!':
            self.error('unexpected call to parse_html_declaration()')
        if rawdata[i:i+4] == '&lt;!--':
            # this case is actually already handled in goahead()
            return self.parse_comment(i)
        elif rawdata[i:i+3] == '&lt;![':
            return self.parse_marked_section(i)
        elif rawdata[i:i+9].lower() == '&lt;!doctype':
            # find the closing &gt;
            gtpos = rawdata.find('&gt;', i+9)
            if gtpos == -1:
                return -1
            self.handle_decl(rawdata[i+2:gtpos])
            return gtpos+1
        else:
            return self.parse_bogus_comment(i)

    # Internal -- parse bogus comment, return length or -1 if not terminated
    # see http://www.w3.org/TR/html5/tokenization.html#bogus-comment-state
    def parse_bogus_comment(self, i, report=1):
        rawdata = self.rawdata
        if rawdata[i:i+2] not in ('&lt;!', '&lt;/'):
            self.error('unexpected call to parse_comment()')
        pos = rawdata.find('&gt;', i+2)
        if pos == -1:
            return -1
        if report:
            self.handle_comment(rawdata[i+2:pos])
        return pos + 1

    # Internal -- parse processing instr, return end or -1 if not terminated
    def parse_pi(self, i):
        rawdata = self.rawdata
        assert rawdata[i:i+2] == '&lt;?', 'unexpected call to parse_pi()'
        match = piclose.search(rawdata, i+2) # &gt;
        if not match:
            return -1
        j = match.start()
        self.handle_pi(rawdata[i+2: j])
        j = match.end()
        return j

    # Internal -- handle starttag, return end or -1 if not terminated
    def parse_starttag(self, i):
        self.__starttag_text = None
        endpos = self.check_for_whole_start_tag(i)
        if endpos &lt; 0:
            return endpos
        rawdata = self.rawdata
        self.__starttag_text = rawdata[i:endpos]

        # Now parse the data between i+1 and j into a tag and attrs
        attrs = []
        match = tagfind.match(rawdata, i+1)
        assert match, 'unexpected call to parse_starttag()'
        k = match.end()
        self.lasttag = tag = match.group(1).lower()

        while k &lt; endpos:
            m = attrfind.match(rawdata, k)
            if not m:
                break
            attrname, rest, attrvalue = m.group(1, 2, 3)
            if not rest:
                attrvalue = None
            elif attrvalue[:1] == '\'' == attrvalue[-1:] or \
                 attrvalue[:1] == '&quot;' == attrvalue[-1:]:
                attrvalue = attrvalue[1:-1]
            if attrvalue:
                attrvalue = self.unescape(attrvalue)
            attrs.append((attrname.lower(), attrvalue))
            k = m.end()

        end = rawdata[k:endpos].strip()
        if end not in (&quot;&gt;&quot;, &quot;/&gt;&quot;):
            lineno, offset = self.getpos()
            if &quot;\n&quot; in self.__starttag_text:
                lineno = lineno + self.__starttag_text.count(&quot;\n&quot;)
                offset = len(self.__starttag_text) \
                         - self.__starttag_text.rfind(&quot;\n&quot;)
            else:
                offset = offset + len(self.__starttag_text)
            self.handle_data(rawdata[i:endpos])
            return endpos
        if end.endswith('/&gt;'):
            # XHTML-style empty tag: &lt;span attr=&quot;value&quot; /&gt;
            self.handle_startendtag(tag, attrs)
        else:
            self.handle_starttag(tag, attrs)
            if tag in self.CDATA_CONTENT_ELEMENTS:
                self.set_cdata_mode(tag)
        return endpos

    # Internal -- check to see if we have a complete starttag; return end
    # or -1 if incomplete.
    def check_for_whole_start_tag(self, i):
        rawdata = self.rawdata
        m = locatestarttagend.match(rawdata, i)
        if m:
            j = m.end()
            next = rawdata[j:j+1]
            if next == &quot;&gt;&quot;:
                return j + 1
            if next == &quot;/&quot;:
                if rawdata.startswith(&quot;/&gt;&quot;, j):
                    return j + 2
                if rawdata.startswith(&quot;/&quot;, j):
                    # buffer boundary
                    return -1
                # else bogus input
                self.updatepos(i, j + 1)
                self.error(&quot;malformed empty start tag&quot;)
            if next == &quot;&quot;:
                # end of input
                return -1
            if next in (&quot;abcdefghijklmnopqrstuvwxyz=/&quot;
                        &quot;ABCDEFGHIJKLMNOPQRSTUVWXYZ&quot;):
                # end of input in or before attribute value, or we have the
                # '/' from a '/&gt;' ending
                return -1
            if j &gt; i:
                return j
            else:
                return i + 1
        raise AssertionError(&quot;we should not get here!&quot;)

    # Internal -- parse endtag, return end or -1 if incomplete
    def parse_endtag(self, i):
        rawdata = self.rawdata
        assert rawdata[i:i+2] == &quot;&lt;/&quot;, &quot;unexpected call to parse_endtag&quot;
        match = endendtag.search(rawdata, i+1) # &gt;
        if not match:
            return -1
        gtpos = match.end()
        match = endtagfind.match(rawdata, i) # &lt;/ + tag + &gt;
        if not match:
            if self.cdata_elem is not None:
                self.handle_data(rawdata[i:gtpos])
                return gtpos
            # find the name: w3.org/TR/html5/tokenization.html#tag-name-state
            namematch = tagfind.match(rawdata, i+2)
            if not namematch:
                # w3.org/TR/html5/tokenization.html#end-tag-open-state
                if rawdata[i:i+3] == '&lt;/&gt;':
                    return i+3
                else:
                    return self.parse_bogus_comment(i)
            tagname = namematch.group(1).lower()
            # consume and ignore other stuff between the name and the &gt;
            # Note: this is not 100% correct, since we might have things like
            # &lt;/tag attr=&quot;&gt;&quot;&gt;, but looking for &gt; after tha name should cover
            # most of the cases and is much simpler
            gtpos = rawdata.find('&gt;', namematch.end())
            self.handle_endtag(tagname)
            return gtpos+1

        elem = match.group(1).lower() # script or style
        if self.cdata_elem is not None:
            if elem != self.cdata_elem:
                self.handle_data(rawdata[i:gtpos])
                return gtpos

        self.handle_endtag(elem)
        self.clear_cdata_mode()
        return gtpos

    # Overridable -- finish processing of start+end tag: &lt;tag.../&gt;
    def handle_startendtag(self, tag, attrs):
        self.handle_starttag(tag, attrs)
        self.handle_endtag(tag)

    # Overridable -- handle start tag
    def handle_starttag(self, tag, attrs):
        pass

    # Overridable -- handle end tag
    def handle_endtag(self, tag):
        pass

    # Overridable -- handle character reference
    def handle_charref(self, name):
        pass

    # Overridable -- handle entity reference
    def handle_entityref(self, name):
        pass

    # Overridable -- handle data
    def handle_data(self, data):
        pass

    # Overridable -- handle comment
    def handle_comment(self, data):
        pass

    # Overridable -- handle declaration
    def handle_decl(self, decl):
        pass

    # Overridable -- handle processing instruction
    def handle_pi(self, data):
        pass

    def unknown_decl(self, data):
        pass

    # Internal -- helper to remove special character quoting
    entitydefs = None
    def unescape(self, s):
        if '&amp;' not in s:
            return s
        def replaceEntities(s):
            s = s.groups()[0]
            try:
                if s[0] == &quot;#&quot;:
                    s = s[1:]
                    if s[0] in ['x','X']:
                        c = int(s[1:], 16)
                    else:
                        c = int(s)
                    return unichr(c)
            except ValueError:
                return '&amp;#'+s+';'
            else:
                # Cannot use name2codepoint directly, because HTMLParser supports apos,
                # which is not part of HTML 4
                if HTMLParser.entitydefs is None:
                    import htmlentitydefs
                    entitydefs = {'apos':u&quot;'&quot;}
                    for k, v in htmlentitydefs.name2codepoint.iteritems():
                        entitydefs[k] = unichr(v)
                    HTMLParser.entitydefs = entitydefs
                try:
                    return self.entitydefs[s]
                except KeyError:
                    return '&amp;'+s+';'

        return re.sub(r&quot;&amp;(#?[xX]?(?:[0-9a-fA-F]+|\w{1,8}));&quot;, replaceEntities, s)
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