先来大致看看HTMLParser的源代码吧：
"""A parser for HTML and XHTML."""
# 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('[&<]')
interesting_cdata = re.compile(r'<(/|\Z)')
incomplete = re.compile('&[a-zA-Z#]')
entityref = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]')
charref = re.compile('&#(?:[0-9]+|[xX][0-9a-fA-F]+)[^0-9a-fA-F]')
starttagopen = re.compile('<[a-zA-Z]')
piclose = re.compile('>')
commentclose = re.compile(r'--\s*>')
tagfind = re.compile('[a-zA-Z][-.a-zA-Z0-9:_]*')
attrfind = re.compile(
r'\s*([a-zA-Z_][-.:a-zA-Z_0-9]*)(\s*=\s*'
r'(\'[^\']*\'|"[^"]*"|[-a-zA-Z0-9./,:;+*%?!&$\(\)_#=~@]*))?')
locatestarttagend = re.compile(r"""
<[a-zA-Z][-.a-zA-Z0-9:_]* # tag name
(?:\s+ # whitespace before attribute name
(?:[a-zA-Z_][-.:a-zA-Z0-9_]* # attribute name
(?:\s*=\s* # value indicator
(?:'[^']*' # LITA-enclosed value
|\"[^\"]*\" # LIT-enclosed value
|[^'\">\s]+ # bare value
)
)?
)
)*
\s* # trailing whitespace
""", re.VERBOSE)
endendtag = re.compile('>')
endtagfind = re.compile('</\s*([a-zA-Z][-.a-zA-Z0-9:_]*)\s*>')
class HTMLParseError(Exception):
"""Exception raised for all parse errors."""
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 + ", at line %d" % self.lineno
if self.offset is not None:
result = result + ", column %d" % (self.offset + 1)
return result
class HTMLParser(markupbase.ParserBase):
"""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.
"""
CDATA_CONTENT_ELEMENTS = ("script", "style")
def __init__(self):
"""Initialize and reset this instance."""
self.reset()
def reset(self):
"""Reset this instance. Loses all unprocessed data."""
self.rawdata = ''
self.lasttag = '???'
self.interesting = interesting_normal
markupbase.ParserBase.reset(self)
def feed(self, data):
"""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').
"""
self.rawdata = self.rawdata + data
self.goahead(0)
def close(self):
"""Handle any buffered data."""
self.goahead(1)
def error(self, message):
raise HTMLParseError(message, self.getpos())
__starttag_text = None
def get_starttag_text(self):
"""Return full source of start tag: '<...>'."""
return self.__starttag_text
def set_cdata_mode(self):
self.interesting = interesting_cdata
def clear_cdata_mode(self):
self.interesting = interesting_normal
# 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 < n:
match = self.interesting.search(rawdata, i) # < or &
if match:
j = match.start()
else:
j = n
if i < j: self.handle_data(rawdata[i:j])
i = self.updatepos(i, j)
if i == n: break
startswith = rawdata.startswith
if startswith('<', i):
if starttagopen.match(rawdata, i): # < + letter
k = self.parse_starttag(i)
elif startswith("</", i):
k = self.parse_endtag(i)
elif startswith("<!--", i):
k = self.parse_comment(i)
elif startswith("<?", i):
k = self.parse_pi(i)
elif startswith("<!", i):
k = self.parse_declaration(i)
elif (i + 1) < n:
self.handle_data("<")
k = i + 1
else:
break
if k < 0:
if end:
self.error("EOF in middle of construct")
break
i = self.updatepos(i, k)
elif startswith("&#", 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 ";" in rawdata[i:]: #bail by consuming &#
self.handle_data(rawdata[0:2])
i = self.updatepos(i, 2)
break
elif startswith('&', 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("EOF in middle of entity or char ref")
# incomplete
break
elif (i + 1) < n:
# not the end of the buffer, and can't be confused
# with some other construct
self.handle_data("&")
i = self.updatepos(i, i + 1)
else:
break
else:
assert 0, "interesting.search() lied"
# end while
if end and i < n:
self.handle_data(rawdata[i:n])
i = self.updatepos(i, n)
self.rawdata = rawdata[i:]
# Internal -- parse processing instr, return end or -1 if not terminated
def parse_pi(self, i):
rawdata = self.rawdata
assert rawdata[i:i+2] == '<?', 'unexpected call to parse_pi()'
match = piclose.search(rawdata, i+2) # >
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 < 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 = rawdata[i+1:k].lower()
while k < 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] == '"' == attrvalue[-1:]:
attrvalue = attrvalue[1:-1]
attrvalue = self.unescape(attrvalue)
attrs.append((attrname.lower(), attrvalue))
k = m.end()
end = rawdata[k:endpos].strip()
if end not in (">", "/>"):
lineno, offset = self.getpos()
if "\n" in self.__starttag_text:
lineno = lineno + self.__starttag_text.count("\n")
offset = len(self.__starttag_text) \
- self.__starttag_text.rfind("\n")
else:
offset = offset + len(self.__starttag_text)
self.error("junk characters in start tag: %r"
% (rawdata[k:endpos][:20],))
if end.endswith('/>'):
# XHTML-style empty tag: <span attr="value" />
self.handle_startendtag(tag, attrs)
else:
self.handle_starttag(tag, attrs)
if tag in self.CDATA_CONTENT_ELEMENTS:
self.set_cdata_mode()
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 == ">":
return j + 1
if next == "/":
if rawdata.startswith("/>", j):
return j + 2
if rawdata.startswith("/", j):
# buffer boundary
return -1
# else bogus input
self.updatepos(i, j + 1)
self.error("malformed empty start tag")
if next == "":
# end of input
return -1
if next in ("abcdefghijklmnopqrstuvwxyz=/"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"):
# end of input in or before attribute value, or we have the
# '/' from a '/>' ending
return -1
self.updatepos(i, j)
self.error("malformed start tag")
raise AssertionError("we should not get here!")
# Internal -- parse endtag, return end or -1 if incomplete
def parse_endtag(self, i):
rawdata = self.rawdata
assert rawdata[i:i+2] == "</", "unexpected call to parse_endtag"
match = endendtag.search(rawdata, i+1) # >
if not match:
return -1
j = match.end()
match = endtagfind.match(rawdata, i) # </ + tag + >
if not match:
self.error("bad end tag: %r" % (rawdata[i:j],))
tag = match.group(1)
self.handle_endtag(tag.lower())
self.clear_cdata_mode()
return j
# Overridable -- finish processing of start+end tag: <tag.../>
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):
self.error("unknown declaration: %r" % (data,))
# Internal -- helper to remove special character quoting
entitydefs = None
def unescape(self, s):
if '&' not in s:
return s
def replaceEntities(s):
s = s.groups()[0]
if s[0] == "#":
s = s[1:]
if s[0] in ['x','X']:
c = int(s[1:], 16)
else:
c = int(s)
return unichr(c)
else:
# Cannot use name2codepoint directly, because HTMLParser supports apos,
# which is not part of HTML 4
import htmlentitydefs
if HTMLParser.entitydefs is None:
entitydefs = HTMLParser.entitydefs = {'apos':u"'"}
for k, v in htmlentitydefs.name2codepoint.iteritems():
entitydefs[k] = unichr(v)
try:
return self.entitydefs[s]
except KeyError:
return '&'+s+';'
return re.sub(r"&(#?[xX]?(?:[0-9a-fA-F]+|\w{1,8}));", replaceEntities, s)
大家可以看到，其实内部的很多的方法都是没有实现的，所以需要我们继承这个类，自己去实现一些方法。关于HTMLParser的方法，大家可以参考官方文档：
http://docs.python.org/library/htmlparser.html#HTMLParser.HTMLParser （英文，笔者没有多少时间去翻译这些）
另外，给一个例子大家对照着看看，我相信这么简单的例子，大家都能看懂的。
假设我们要处理的文件在d盘根目录下，名字为hello.html,文件的内容为：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>Rollen Holt - cnblogs</title> <meta name="keywords" content="Rollen Holt,rollenholt" /> <link type="text/css" rel="stylesheet" href="http://www.cnblogs.com/css/common.css"/> <link id="MainCss" type="text/css" rel="stylesheet" href="http://www.cnblogs.com/Skins/kubrick/style.css"/> <link type="text/css" rel="stylesheet" href="http://www.cnblogs.com/css/common2.css"/> <link type="text/css" rel="stylesheet" href="http://common.cnblogs.com/css/shCore.css"/> <link type="text/css" rel="stylesheet" href="http://common.cnblogs.com/css/shThemeDefault.css"/> <link title="RSS" type="application/rss+xml" rel="alternate" href="http://www.cnblogs.com/rollenholt/rss"/> <link title="RSD" type="application/rsd+xml" rel="EditURI" href="http://www.cnblogs.com/rollenholt/rsd.xml"/> <link type="application/wlwmanifest+xml" rel="wlwmanifest" href="http://www.cnblogs.com/rollenholt/wlwmanifest.xml"/> <script src="http://common.cnblogs.com/script/jquery.js" type="text/javascript"></script> <script src="/script/common.js" type="text/javascript"></script> <script src="http://common.cnblogs.com/script/jquery.json-2.2.min.js" type="text/javascript"></script> <script type="text/javascript" src="http://common.cnblogs.com/script/shCore.js"></script> <script type="text/javascript" src="http://common.cnblogs.com/script/shLanguage.js"></script> </head> <body> <a name="top"></a> <form method="post" action="" id="Form1"> <div class="aspNetHidden"> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="" /> </div> </form> </body> </html>
我们的python代码为：
#coding=utf-8
from HTMLParser import HTMLParser
class MyParser(HTMLParser):
"""一个简单的HTMLparser的例子"""
def handle_decl(self, decl):
"""处理头文档"""
HTMLParser.handle_decl(self, decl)
print decl
def handle_starttag(self, tag, attrs):
"""处理起始标签"""
HTMLParser.handle_starttag(self, tag, attrs)
if not HTMLParser.get_starttag_text(self).endswith("/>"):
print "<",tag,">"
def handle_data(self, data):
"""处理文本元素"""
HTMLParser.handle_data(self, data)
print data,
def handle_endtag(self, tag):
"""处理结束标签"""
HTMLParser.handle_endtag(self, tag)
if not HTMLParser.get_starttag_text(self).endswith("/>"):
print "</",tag,">"
def handle_startendtag(self, tag, attrs):
"""处理自闭标签"""
HTMLParser.handle_startendtag(self, tag, attrs)
print HTMLParser.get_starttag_text(self)
def handle_comment(self, data):
"""处理注释"""
HTMLParser.handle_comment(self, data)
print data
def close(self):
HTMLParser.close(self)
print "parser over"
demo=MyParser()
demo.feed(open("d:\\hello.html").read())
demo.close()
输出的结果为：
DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"
< html >
< head >
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
< title >
Rollen Holt - cnblogs </ title >
<meta name="keywords" content="Rollen Holt,rollenholt" />
<link type="text/css" rel="stylesheet" href="http://www.cnblogs.com/css/common.css"/>
<link id="MainCss" type="text/css" rel="stylesheet" href="http://www.cnblogs.com/Skins/kubrick/style.css"/>
<link type="text/css" rel="stylesheet" href="http://www.cnblogs.com/css/common2.css"/>
<link type="text/css" rel="stylesheet" href="http://common.cnblogs.com/css/shCore.css"/>
<link type="text/css" rel="stylesheet" href="http://common.cnblogs.com/css/shThemeDefault.css"/>
<link title="RSS" type="application/rss+xml" rel="alternate" href="http://www.cnblogs.com/rollenholt/rss"/>
<link title="RSD" type="application/rsd+xml" rel="EditURI" href="http://www.cnblogs.com/rollenholt/rsd.xml"/>
<link type="application/wlwmanifest+xml" rel="wlwmanifest" href="http://www.cnblogs.com/rollenholt/wlwmanifest.xml"/>
< script >
</ script >
< script >
</ script >
< script >
</ script >
< script >
</ script >
< script >
</ script >
</ head >
< body >
< a >
</ a >
< form >
< div >
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="" />
parser over
