Viewing file:  _pullparser.py (13.99 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
"""A simple "pull API" for HTML parsing, after Perl's HTML::TokeParser.
Examples
This program extracts all links from a document. It will print one
line for each link, containing the URL and the textual description
between the <A>...</A> tags:
import pullparser, sys
f = file(sys.argv[1])
p = pullparser.PullParser(f)
for token in p.tags("a"):
if token.type == "endtag": continue
url = dict(token.attrs).get("href", "-")
text = p.get_compressed_text(endat=("endtag", "a"))
print "%s\t%s" % (url, text)
This program extracts the <TITLE> from the document:
import pullparser, sys
f = file(sys.argv[1])
p = pullparser.PullParser(f)
if p.get_tag("title"):
title = p.get_compressed_text()
print "Title: %s" % title
Copyright 2003-2006 John J. Lee <jjl@pobox.com>
Copyright 1998-2001 Gisle Aas (original libwww-perl code)
This code is free software; you can redistribute it and/or modify it
under the terms of the BSD or ZPL 2.1 licenses.
"""
import re, htmlentitydefs
import sgmllib, HTMLParser
from xml.sax import saxutils
from _html import unescape, unescape_charref
class NoMoreTokensError(Exception): pass
class Token:
"""Represents an HTML tag, declaration, processing instruction etc.
Behaves as both a tuple-like object (ie. iterable) and has attributes
.type, .data and .attrs.
>>> t = Token("starttag", "a", [("href", "http://www.python.org/")])
>>> t == ("starttag", "a", [("href", "http://www.python.org/")])
True
>>> (t.type, t.data) == ("starttag", "a")
True
>>> t.attrs == [("href", "http://www.python.org/")]
True
Public attributes
type: one of "starttag", "endtag", "startendtag", "charref", "entityref",
"data", "comment", "decl", "pi", after the corresponding methods of
HTMLParser.HTMLParser
data: For a tag, the tag name; otherwise, the relevant data carried by the
tag, as a string
attrs: list of (name, value) pairs representing HTML attributes
(or None if token does not represent an opening tag)
"""
def __init__(self, type, data, attrs=None):
self.type = type
self.data = data
self.attrs = attrs
def __iter__(self):
return iter((self.type, self.data, self.attrs))
def __eq__(self, other):
type, data, attrs = other
if (self.type == type and
self.data == data and
self.attrs == attrs):
return True
else:
return False
def __ne__(self, other): return not self.__eq__(other)
def __repr__(self):
args = ", ".join(map(repr, [self.type, self.data, self.attrs]))
return self.__class__.__name__+"(%s)" % args
def __str__(self):
"""
>>> print Token("starttag", "br")
<br>
>>> print Token("starttag", "a",
... [("href", "http://www.python.org/"), ("alt", '"foo"')])
<a href="http://www.python.org/" alt='"foo"'>
>>> print Token("startendtag", "br")
<br />
>>> print Token("startendtag", "br", [("spam", "eggs")])
<br spam="eggs" />
>>> print Token("endtag", "p")
</p>
>>> print Token("charref", "38")
&
>>> print Token("entityref", "amp")
&
>>> print Token("data", "foo\\nbar")
foo
bar
>>> print Token("comment", "Life is a bowl\\nof cherries.")
<!--Life is a bowl
of cherries.-->
>>> print Token("decl", "decl")
<!decl>
>>> print Token("pi", "pi")
<?pi>
"""
if self.attrs is not None:
attrs = "".join([" %s=%s" % (k, saxutils.quoteattr(v)) for
k, v in self.attrs])
else:
attrs = ""
if self.type == "starttag":
return "<%s%s>" % (self.data, attrs)
elif self.type == "startendtag":
return "<%s%s />" % (self.data, attrs)
elif self.type == "endtag":
return "</%s>" % self.data
elif self.type == "charref":
return "&#%s;" % self.data
elif self.type == "entityref":
return "&%s;" % self.data
elif self.type == "data":
return self.data
elif self.type == "comment":
return "<!--%s-->" % self.data
elif self.type == "decl":
return "<!%s>" % self.data
elif self.type == "pi":
return "<?%s>" % self.data
assert False
def iter_until_exception(fn, exception, *args, **kwds):
while 1:
try:
yield fn(*args, **kwds)
except exception:
raise StopIteration
class _AbstractParser:
chunk = 1024
compress_re = re.compile(r"\s+")
def __init__(self, fh, textify={"img": "alt", "applet": "alt"},
encoding="ascii", entitydefs=None):
"""
fh: file-like object (only a .read() method is required) from which to
read HTML to be parsed
textify: mapping used by .get_text() and .get_compressed_text() methods
to represent opening tags as text
encoding: encoding used to encode numeric character references by
.get_text() and .get_compressed_text() ("ascii" by default)
entitydefs: mapping like {"amp": "&", ...} containing HTML entity
definitions (a sensible default is used). This is used to unescape
entities in .get_text() (and .get_compressed_text()) and attribute
values. If the encoding can not represent the character, the entity
reference is left unescaped. Note that entity references (both
numeric - e.g. { or ઼ - and non-numeric - e.g. &) are
unescaped in attribute values and the return value of .get_text(), but
not in data outside of tags. Instead, entity references outside of
tags are represented as tokens. This is a bit odd, it's true :-/
If the element name of an opening tag matches a key in the textify
mapping then that tag is converted to text. The corresponding value is
used to specify which tag attribute to obtain the text from. textify
maps from element names to either:
- an HTML attribute name, in which case the HTML attribute value is
used as its text value along with the element name in square
brackets (eg."alt text goes here[IMG]", or, if the alt attribute
were missing, just "[IMG]")
- a callable object (eg. a function) which takes a Token and returns
the string to be used as its text value
If textify has no key for an element name, nothing is substituted for
the opening tag.
Public attributes:
encoding and textify: see above
"""
self._fh = fh
self._tokenstack = [] # FIFO
self.textify = textify
self.encoding = encoding
if entitydefs is None:
entitydefs = htmlentitydefs.name2codepoint
self._entitydefs = entitydefs
def __iter__(self): return self
def tags(self, *names):
return iter_until_exception(self.get_tag, NoMoreTokensError, *names)
def tokens(self, *tokentypes):
return iter_until_exception(self.get_token, NoMoreTokensError,
*tokentypes)
def next(self):
try:
return self.get_token()
except NoMoreTokensError:
raise StopIteration()
def get_token(self, *tokentypes):
"""Pop the next Token object from the stack of parsed tokens.
If arguments are given, they are taken to be token types in which the
caller is interested: tokens representing other elements will be
skipped. Element names must be given in lower case.
Raises NoMoreTokensError.
"""
while 1:
while self._tokenstack:
token = self._tokenstack.pop(0)
if tokentypes:
if token.type in tokentypes:
return token
else:
return token
data = self._fh.read(self.chunk)
if not data:
raise NoMoreTokensError()
self.feed(data)
def unget_token(self, token):
"""Push a Token back onto the stack."""
self._tokenstack.insert(0, token)
def get_tag(self, *names):
"""Return the next Token that represents an opening or closing tag.
If arguments are given, they are taken to be element names in which the
caller is interested: tags representing other elements will be skipped.
Element names must be given in lower case.
Raises NoMoreTokensError.
"""
while 1:
tok = self.get_token()
if tok.type not in ["starttag", "endtag", "startendtag"]:
continue
if names:
if tok.data in names:
return tok
else:
return tok
def get_text(self, endat=None):
"""Get some text.
endat: stop reading text at this tag (the tag is included in the
returned text); endtag is a tuple (type, name) where type is
"starttag", "endtag" or "startendtag", and name is the element name of
the tag (element names must be given in lower case)
If endat is not given, .get_text() will stop at the next opening or
closing tag, or when there are no more tokens (no exception is raised).
Note that .get_text() includes the text representation (if any) of the
opening tag, but pushes the opening tag back onto the stack. As a
result, if you want to call .get_text() again, you need to call
.get_tag() first (unless you want an empty string returned when you
next call .get_text()).
Entity references are translated using the value of the entitydefs
constructor argument (a mapping from names to characters like that
provided by the standard module htmlentitydefs). Named entity
references that are not in this mapping are left unchanged.
The textify attribute is used to translate opening tags into text: see
the class docstring.
"""
text = []
tok = None
while 1:
try:
tok = self.get_token()
except NoMoreTokensError:
# unget last token (not the one we just failed to get)
if tok: self.unget_token(tok)
break
if tok.type == "data":
text.append(tok.data)
elif tok.type == "entityref":
t = unescape("&%s;"%tok.data, self._entitydefs, self.encoding)
text.append(t)
elif tok.type == "charref":
t = unescape_charref(tok.data, self.encoding)
text.append(t)
elif tok.type in ["starttag", "endtag", "startendtag"]:
tag_name = tok.data
if tok.type in ["starttag", "startendtag"]:
alt = self.textify.get(tag_name)
if alt is not None:
if callable(alt):
text.append(alt(tok))
elif tok.attrs is not None:
for k, v in tok.attrs:
if k == alt:
text.append(v)
text.append("[%s]" % tag_name.upper())
if endat is None or endat == (tok.type, tag_name):
self.unget_token(tok)
break
return "".join(text)
def get_compressed_text(self, *args, **kwds):
"""
As .get_text(), but collapses each group of contiguous whitespace to a
single space character, and removes all initial and trailing
whitespace.
"""
text = self.get_text(*args, **kwds)
text = text.strip()
return self.compress_re.sub(" ", text)
def handle_startendtag(self, tag, attrs):
self._tokenstack.append(Token("startendtag", tag, attrs))
def handle_starttag(self, tag, attrs):
self._tokenstack.append(Token("starttag", tag, attrs))
def handle_endtag(self, tag):
self._tokenstack.append(Token("endtag", tag))
def handle_charref(self, name):
self._tokenstack.append(Token("charref", name))
def handle_entityref(self, name):
self._tokenstack.append(Token("entityref", name))
def handle_data(self, data):
self._tokenstack.append(Token("data", data))
def handle_comment(self, data):
self._tokenstack.append(Token("comment", data))
def handle_decl(self, decl):
self._tokenstack.append(Token("decl", decl))
def unknown_decl(self, data):
# XXX should this call self.error instead?
#self.error("unknown declaration: " + `data`)
self._tokenstack.append(Token("decl", data))
def handle_pi(self, data):
self._tokenstack.append(Token("pi", data))
def unescape_attr(self, name):
return unescape(name, self._entitydefs, self.encoding)
def unescape_attrs(self, attrs):
escaped_attrs = []
for key, val in attrs:
escaped_attrs.append((key, self.unescape_attr(val)))
return escaped_attrs
class PullParser(_AbstractParser, HTMLParser.HTMLParser):
def __init__(self, *args, **kwds):
HTMLParser.HTMLParser.__init__(self)
_AbstractParser.__init__(self, *args, **kwds)
def unescape(self, name):
# Use the entitydefs passed into constructor, not
# HTMLParser.HTMLParser's entitydefs.
return self.unescape_attr(name)
class TolerantPullParser(_AbstractParser, sgmllib.SGMLParser):
def __init__(self, *args, **kwds):
sgmllib.SGMLParser.__init__(self)
_AbstractParser.__init__(self, *args, **kwds)
def unknown_starttag(self, tag, attrs):
attrs = self.unescape_attrs(attrs)
self._tokenstack.append(Token("starttag", tag, attrs))
def unknown_endtag(self, tag):
self._tokenstack.append(Token("endtag", tag))
def _test():
import doctest, _pullparser
return doctest.testmod(_pullparser)
if __name__ == "__main__":
_test()
|