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477 lines
15 KiB
Python
477 lines
15 KiB
Python
# A parser for SGML, using the derived class as static DTD.
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# XXX This only supports those SGML features used by HTML.
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# XXX There should be a way to distinguish between PCDATA (parsed
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# character data -- the normal case), RCDATA (replaceable character
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# data -- only char and entity references and end tags are special)
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# and CDATA (character data -- only end tags are special).
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import re
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import string
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# Regular expressions used for parsing
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interesting = re.compile('[&<]')
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incomplete = re.compile('&([a-zA-Z][a-zA-Z0-9]*|#[0-9]*)?|'
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'<([a-zA-Z][^<>]*|'
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'/([a-zA-Z][^<>]*)?|'
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'![^<>]*)?')
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entityref = re.compile('&([a-zA-Z][-.a-zA-Z0-9]*)[^a-zA-Z0-9]')
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charref = re.compile('&#([0-9]+)[^0-9]')
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starttagopen = re.compile('<[>a-zA-Z]')
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shorttagopen = re.compile('<[a-zA-Z][-.a-zA-Z0-9]*/')
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shorttag = re.compile('<([a-zA-Z][-.a-zA-Z0-9]*)/([^/]*)/')
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piopen = re.compile('<\?')
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piclose = re.compile('>')
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endtagopen = re.compile('</[<>a-zA-Z]')
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endbracket = re.compile('[<>]')
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special = re.compile('<![^<>]*>')
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commentopen = re.compile('<!--')
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commentclose = re.compile('--[%s]*>' % string.whitespace)
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tagfind = re.compile('[a-zA-Z][-.a-zA-Z0-9]*')
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attrfind = re.compile(
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'[%s]+([a-zA-Z_][-.a-zA-Z_0-9]*)' % string.whitespace
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+ ('([%s]*=[%s]*' % (string.whitespace, string.whitespace))
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+ r'(\'[^\']*\'|"[^"]*"|[-a-zA-Z0-9./:+*%?!\(\)_#=~]*))?')
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# SGML parser base class -- find tags and call handler functions.
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# Usage: p = SGMLParser(); p.feed(data); ...; p.close().
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# The dtd is defined by deriving a class which defines methods
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# with special names to handle tags: start_foo and end_foo to handle
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# <foo> and </foo>, respectively, or do_foo to handle <foo> by itself.
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# (Tags are converted to lower case for this purpose.) The data
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# between tags is passed to the parser by calling self.handle_data()
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# with some data as argument (the data may be split up in arbutrary
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# chunks). Entity references are passed by calling
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# self.handle_entityref() with the entity reference as argument.
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class SGMLParser:
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# Interface -- initialize and reset this instance
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def __init__(self, verbose=0):
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self.verbose = verbose
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self.reset()
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# Interface -- reset this instance. Loses all unprocessed data
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def reset(self):
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self.rawdata = ''
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self.stack = []
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self.lasttag = '???'
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self.nomoretags = 0
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self.literal = 0
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# For derived classes only -- enter literal mode (CDATA) till EOF
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def setnomoretags(self):
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self.nomoretags = self.literal = 1
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# For derived classes only -- enter literal mode (CDATA)
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def setliteral(self, *args):
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self.literal = 1
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# Interface -- feed some data to the parser. Call this as
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# often as you want, with as little or as much text as you
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# want (may include '\n'). (This just saves the text, all the
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# processing is done by goahead().)
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def feed(self, data):
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self.rawdata = self.rawdata + data
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self.goahead(0)
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# Interface -- handle the remaining data
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def close(self):
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self.goahead(1)
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# Internal -- handle data as far as reasonable. May leave state
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# and data to be processed by a subsequent call. If 'end' is
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# true, force handling all data as if followed by EOF marker.
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def goahead(self, end):
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rawdata = self.rawdata
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i = 0
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n = len(rawdata)
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while i < n:
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if self.nomoretags:
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self.handle_data(rawdata[i:n])
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i = n
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break
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match = interesting.search(rawdata, i)
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if match: j = match.start(0)
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else: j = n
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if i < j: self.handle_data(rawdata[i:j])
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i = j
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if i == n: break
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if rawdata[i] == '<':
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if starttagopen.match(rawdata, i):
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if self.literal:
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self.handle_data(rawdata[i])
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i = i+1
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continue
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k = self.parse_starttag(i)
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if k < 0: break
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i = k
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continue
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if endtagopen.match(rawdata, i):
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k = self.parse_endtag(i)
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if k < 0: break
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i = k
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self.literal = 0
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continue
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if commentopen.match(rawdata, i):
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if self.literal:
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self.handle_data(rawdata[i])
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i = i+1
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continue
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k = self.parse_comment(i)
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if k < 0: break
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i = i+k
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continue
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if piopen.match(rawdata, i):
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if self.literal:
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self.handle_data(rawdata[i])
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i = i+1
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continue
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k = self.parse_pi(i)
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if k < 0: break
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i = i+k
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continue
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match = special.match(rawdata, i)
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if match:
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if self.literal:
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self.handle_data(rawdata[i])
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i = i+1
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continue
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i = match.end(0)
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continue
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elif rawdata[i] == '&':
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match = charref.match(rawdata, i)
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if match:
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name = match.group(1)
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self.handle_charref(name)
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i = match.end(0)
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if rawdata[i-1] != ';': i = i-1
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continue
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match = entityref.match(rawdata, i)
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if match:
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name = match.group(1)
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self.handle_entityref(name)
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i = match.end(0)
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if rawdata[i-1] != ';': i = i-1
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continue
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else:
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raise RuntimeError, 'neither < nor & ??'
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# We get here only if incomplete matches but
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# nothing else
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match = incomplete.match(rawdata, i)
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if not match:
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self.handle_data(rawdata[i])
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i = i+1
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continue
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j = match.end(0)
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if j == n:
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break # Really incomplete
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self.handle_data(rawdata[i:j])
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i = j
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# end while
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if end and i < n:
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self.handle_data(rawdata[i:n])
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i = n
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self.rawdata = rawdata[i:]
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# XXX if end: check for empty stack
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# Internal -- parse comment, return length or -1 if not terminated
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def parse_comment(self, i):
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rawdata = self.rawdata
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if rawdata[i:i+4] <> '<!--':
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raise RuntimeError, 'unexpected call to handle_comment'
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match = commentclose.search(rawdata, i+4)
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if not match:
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return -1
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j = match.start(0)
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self.handle_comment(rawdata[i+4: j])
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j = match.end(0)
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return j-i
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# Internal -- parse processing instr, return length or -1 if not terminated
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def parse_pi(self, i):
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rawdata = self.rawdata
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if rawdata[i:i+2] <> '<?':
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raise RuntimeError, 'unexpected call to handle_pi'
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match = piclose.search(rawdata, i+2)
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if not match:
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return -1
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j = match.start(0)
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self.handle_pi(rawdata[i+2: j])
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j = match.end(0)
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return j-i
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# Internal -- handle starttag, return length or -1 if not terminated
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def parse_starttag(self, i):
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rawdata = self.rawdata
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if shorttagopen.match(rawdata, i):
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# SGML shorthand: <tag/data/ == <tag>data</tag>
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# XXX Can data contain &... (entity or char refs)?
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# XXX Can data contain < or > (tag characters)?
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# XXX Can there be whitespace before the first /?
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match = shorttag.match(rawdata, i)
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if not match:
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return -1
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tag, data = match.group(1, 2)
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tag = string.lower(tag)
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self.finish_shorttag(tag, data)
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k = match.end(0)
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return k
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# XXX The following should skip matching quotes (' or ")
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match = endbracket.search(rawdata, i+1)
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if not match:
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return -1
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j = match.start(0)
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# Now parse the data between i+1 and j into a tag and attrs
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attrs = []
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if rawdata[i:i+2] == '<>':
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# SGML shorthand: <> == <last open tag seen>
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k = j
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tag = self.lasttag
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else:
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match = tagfind.match(rawdata, i+1)
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if not match:
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raise RuntimeError, 'unexpected call to parse_starttag'
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k = match.end(0)
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tag = string.lower(rawdata[i+1:k])
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self.lasttag = tag
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while k < j:
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match = attrfind.match(rawdata, k)
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if not match: break
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attrname, rest, attrvalue = match.group(1, 2, 3)
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if not rest:
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attrvalue = attrname
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elif attrvalue[:1] == '\'' == attrvalue[-1:] or \
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attrvalue[:1] == '"' == attrvalue[-1:]:
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attrvalue = attrvalue[1:-1]
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attrs.append((string.lower(attrname), attrvalue))
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k = match.end(0)
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if rawdata[j] == '>':
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j = j+1
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self.finish_starttag(tag, attrs)
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return j
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# Internal -- parse endtag
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def parse_endtag(self, i):
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rawdata = self.rawdata
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match = endbracket.search(rawdata, i+1)
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if not match:
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return -1
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j = match.start(0)
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tag = string.lower(string.strip(rawdata[i+2:j]))
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if rawdata[j] == '>':
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j = j+1
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self.finish_endtag(tag)
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return j
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# Internal -- finish parsing of <tag/data/ (same as <tag>data</tag>)
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def finish_shorttag(self, tag, data):
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self.finish_starttag(tag, [])
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self.handle_data(data)
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self.finish_endtag(tag)
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# Internal -- finish processing of start tag
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# Return -1 for unknown tag, 0 for open-only tag, 1 for balanced tag
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def finish_starttag(self, tag, attrs):
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try:
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method = getattr(self, 'start_' + tag)
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except AttributeError:
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try:
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method = getattr(self, 'do_' + tag)
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except AttributeError:
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self.unknown_starttag(tag, attrs)
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return -1
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else:
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self.handle_starttag(tag, method, attrs)
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return 0
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else:
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self.stack.append(tag)
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self.handle_starttag(tag, method, attrs)
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return 1
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# Internal -- finish processing of end tag
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def finish_endtag(self, tag):
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if not tag:
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found = len(self.stack) - 1
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if found < 0:
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self.unknown_endtag(tag)
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return
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else:
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if tag not in self.stack:
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try:
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method = getattr(self, 'end_' + tag)
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except AttributeError:
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self.unknown_endtag(tag)
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else:
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self.report_unbalanced(tag)
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return
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found = len(self.stack)
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for i in range(found):
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if self.stack[i] == tag: found = i
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while len(self.stack) > found:
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tag = self.stack[-1]
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try:
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method = getattr(self, 'end_' + tag)
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except AttributeError:
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method = None
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if method:
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self.handle_endtag(tag, method)
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else:
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self.unknown_endtag(tag)
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del self.stack[-1]
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# Overridable -- handle start tag
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def handle_starttag(self, tag, method, attrs):
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method(attrs)
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# Overridable -- handle end tag
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def handle_endtag(self, tag, method):
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method()
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# Example -- report an unbalanced </...> tag.
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def report_unbalanced(self, tag):
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if self.verbose:
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print '*** Unbalanced </' + tag + '>'
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print '*** Stack:', self.stack
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# Example -- handle character reference, no need to override
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def handle_charref(self, name):
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try:
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n = string.atoi(name)
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except string.atoi_error:
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self.unknown_charref(name)
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return
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if not 0 <= n <= 255:
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self.unknown_charref(name)
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return
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self.handle_data(chr(n))
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# Definition of entities -- derived classes may override
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entitydefs = \
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{'lt': '<', 'gt': '>', 'amp': '&', 'quot': '"', 'apos': '\''}
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# Example -- handle entity reference, no need to override
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def handle_entityref(self, name):
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table = self.entitydefs
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if table.has_key(name):
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self.handle_data(table[name])
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else:
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self.unknown_entityref(name)
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return
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# Example -- handle data, should be overridden
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def handle_data(self, data):
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pass
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# Example -- handle comment, could be overridden
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def handle_comment(self, data):
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pass
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# Example -- handle processing instruction, could be overridden
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def handle_pi(self, data):
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pass
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# To be overridden -- handlers for unknown objects
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def unknown_starttag(self, tag, attrs): pass
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def unknown_endtag(self, tag): pass
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def unknown_charref(self, ref): pass
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def unknown_entityref(self, ref): pass
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class TestSGMLParser(SGMLParser):
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def __init__(self, verbose=0):
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self.testdata = ""
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SGMLParser.__init__(self, verbose)
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def handle_data(self, data):
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self.testdata = self.testdata + data
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if len(`self.testdata`) >= 70:
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self.flush()
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def flush(self):
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data = self.testdata
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if data:
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self.testdata = ""
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print 'data:', `data`
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def handle_comment(self, data):
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self.flush()
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r = `data`
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if len(r) > 68:
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r = r[:32] + '...' + r[-32:]
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print 'comment:', r
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def unknown_starttag(self, tag, attrs):
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self.flush()
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if not attrs:
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print 'start tag: <' + tag + '>'
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else:
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print 'start tag: <' + tag,
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for name, value in attrs:
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print name + '=' + '"' + value + '"',
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print '>'
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def unknown_endtag(self, tag):
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self.flush()
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print 'end tag: </' + tag + '>'
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def unknown_entityref(self, ref):
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self.flush()
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print '*** unknown entity ref: &' + ref + ';'
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def unknown_charref(self, ref):
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self.flush()
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print '*** unknown char ref: &#' + ref + ';'
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def close(self):
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SGMLParser.close(self)
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self.flush()
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def test(args = None):
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import sys
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if not args:
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args = sys.argv[1:]
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if args and args[0] == '-s':
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args = args[1:]
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klass = SGMLParser
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else:
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klass = TestSGMLParser
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if args:
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file = args[0]
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else:
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file = 'test.html'
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if file == '-':
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f = sys.stdin
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else:
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try:
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f = open(file, 'r')
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except IOError, msg:
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print file, ":", msg
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sys.exit(1)
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data = f.read()
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if f is not sys.stdin:
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f.close()
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x = klass()
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for c in data:
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x.feed(c)
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x.close()
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if __name__ == '__main__':
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test()
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