You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
273 lines
10 KiB
Python
273 lines
10 KiB
Python
# Natural Language Toolkit: Penn Treebank Reader
|
|
#
|
|
# Copyright (C) 2001-2020 NLTK Project
|
|
# Author: Steven Bird <stevenbird1@gmail.com>
|
|
# Edward Loper <edloper@gmail.com>
|
|
# URL: <http://nltk.org/>
|
|
# For license information, see LICENSE.TXT
|
|
"""
|
|
Corpus reader for corpora that consist of parenthesis-delineated parse trees.
|
|
"""
|
|
|
|
import sys
|
|
|
|
from nltk.tree import Tree
|
|
from nltk.tag import map_tag
|
|
|
|
from nltk.corpus.reader.util import *
|
|
from nltk.corpus.reader.api import *
|
|
|
|
# we use [^\s()]+ instead of \S+? to avoid matching ()
|
|
SORTTAGWRD = re.compile(r"\((\d+) ([^\s()]+) ([^\s()]+)\)")
|
|
TAGWORD = re.compile(r"\(([^\s()]+) ([^\s()]+)\)")
|
|
WORD = re.compile(r"\([^\s()]+ ([^\s()]+)\)")
|
|
EMPTY_BRACKETS = re.compile(r"\s*\(\s*\(")
|
|
|
|
|
|
class BracketParseCorpusReader(SyntaxCorpusReader):
|
|
"""
|
|
Reader for corpora that consist of parenthesis-delineated parse trees,
|
|
like those found in the "combined" section of the Penn Treebank,
|
|
e.g. "(S (NP (DT the) (JJ little) (NN dog)) (VP (VBD barked)))".
|
|
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
root,
|
|
fileids,
|
|
comment_char=None,
|
|
detect_blocks="unindented_paren",
|
|
encoding="utf8",
|
|
tagset=None,
|
|
):
|
|
"""
|
|
:param root: The root directory for this corpus.
|
|
:param fileids: A list or regexp specifying the fileids in this corpus.
|
|
:param comment_char: The character which can appear at the start of
|
|
a line to indicate that the rest of the line is a comment.
|
|
:param detect_blocks: The method that is used to find blocks
|
|
in the corpus; can be 'unindented_paren' (every unindented
|
|
parenthesis starts a new parse) or 'sexpr' (brackets are
|
|
matched).
|
|
:param tagset: The name of the tagset used by this corpus, to be used
|
|
for normalizing or converting the POS tags returned by the
|
|
tagged_...() methods.
|
|
"""
|
|
# FIXME: Why is it inheritting from SyntaxCorpusReader but initializing
|
|
# from CorpusReader?
|
|
CorpusReader.__init__(self, root, fileids, encoding)
|
|
self._comment_char = comment_char
|
|
self._detect_blocks = detect_blocks
|
|
self._tagset = tagset
|
|
|
|
def _read_block(self, stream):
|
|
if self._detect_blocks == "sexpr":
|
|
return read_sexpr_block(stream, comment_char=self._comment_char)
|
|
elif self._detect_blocks == "blankline":
|
|
return read_blankline_block(stream)
|
|
elif self._detect_blocks == "unindented_paren":
|
|
# Tokens start with unindented left parens.
|
|
toks = read_regexp_block(stream, start_re=r"^\(")
|
|
# Strip any comments out of the tokens.
|
|
if self._comment_char:
|
|
toks = [
|
|
re.sub("(?m)^%s.*" % re.escape(self._comment_char), "", tok)
|
|
for tok in toks
|
|
]
|
|
return toks
|
|
else:
|
|
assert 0, "bad block type"
|
|
|
|
def _normalize(self, t):
|
|
# Replace leaves of the form (!), (,), with (! !), (, ,)
|
|
t = re.sub(r"\((.)\)", r"(\1 \1)", t)
|
|
# Replace leaves of the form (tag word root) with (tag word)
|
|
t = re.sub(r"\(([^\s()]+) ([^\s()]+) [^\s()]+\)", r"(\1 \2)", t)
|
|
return t
|
|
|
|
def _parse(self, t):
|
|
try:
|
|
tree = Tree.fromstring(self._normalize(t))
|
|
# If there's an empty node at the top, strip it off
|
|
if tree.label() == '' and len(tree) == 1:
|
|
return tree[0]
|
|
else:
|
|
return tree
|
|
|
|
except ValueError as e:
|
|
sys.stderr.write("Bad tree detected; trying to recover...\n")
|
|
# Try to recover, if we can:
|
|
if e.args == ("mismatched parens",):
|
|
for n in range(1, 5):
|
|
try:
|
|
v = Tree(self._normalize(t + ")" * n))
|
|
sys.stderr.write(
|
|
" Recovered by adding %d close " "paren(s)\n" % n
|
|
)
|
|
return v
|
|
except ValueError:
|
|
pass
|
|
# Try something else:
|
|
sys.stderr.write(" Recovered by returning a flat parse.\n")
|
|
# sys.stderr.write(' '.join(t.split())+'\n')
|
|
return Tree("S", self._tag(t))
|
|
|
|
def _tag(self, t, tagset=None):
|
|
tagged_sent = [(w, p) for (p, w) in TAGWORD.findall(self._normalize(t))]
|
|
if tagset and tagset != self._tagset:
|
|
tagged_sent = [
|
|
(w, map_tag(self._tagset, tagset, p)) for (w, p) in tagged_sent
|
|
]
|
|
return tagged_sent
|
|
|
|
def _word(self, t):
|
|
return WORD.findall(self._normalize(t))
|
|
|
|
|
|
class CategorizedBracketParseCorpusReader(
|
|
CategorizedCorpusReader, BracketParseCorpusReader
|
|
):
|
|
"""
|
|
A reader for parsed corpora whose documents are
|
|
divided into categories based on their file identifiers.
|
|
@author: Nathan Schneider <nschneid@cs.cmu.edu>
|
|
"""
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
"""
|
|
Initialize the corpus reader. Categorization arguments
|
|
(C{cat_pattern}, C{cat_map}, and C{cat_file}) are passed to
|
|
the L{CategorizedCorpusReader constructor
|
|
<CategorizedCorpusReader.__init__>}. The remaining arguments
|
|
are passed to the L{BracketParseCorpusReader constructor
|
|
<BracketParseCorpusReader.__init__>}.
|
|
"""
|
|
CategorizedCorpusReader.__init__(self, kwargs)
|
|
BracketParseCorpusReader.__init__(self, *args, **kwargs)
|
|
|
|
def _resolve(self, fileids, categories):
|
|
if fileids is not None and categories is not None:
|
|
raise ValueError("Specify fileids or categories, not both")
|
|
if categories is not None:
|
|
return self.fileids(categories)
|
|
else:
|
|
return fileids
|
|
|
|
def raw(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.raw(self, self._resolve(fileids, categories))
|
|
|
|
def words(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.words(self, self._resolve(fileids, categories))
|
|
|
|
def sents(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.sents(self, self._resolve(fileids, categories))
|
|
|
|
def paras(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.paras(self, self._resolve(fileids, categories))
|
|
|
|
def tagged_words(self, fileids=None, categories=None, tagset=None):
|
|
return BracketParseCorpusReader.tagged_words(
|
|
self, self._resolve(fileids, categories), tagset
|
|
)
|
|
|
|
def tagged_sents(self, fileids=None, categories=None, tagset=None):
|
|
return BracketParseCorpusReader.tagged_sents(
|
|
self, self._resolve(fileids, categories), tagset
|
|
)
|
|
|
|
def tagged_paras(self, fileids=None, categories=None, tagset=None):
|
|
return BracketParseCorpusReader.tagged_paras(
|
|
self, self._resolve(fileids, categories), tagset
|
|
)
|
|
|
|
def parsed_words(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.parsed_words(
|
|
self, self._resolve(fileids, categories)
|
|
)
|
|
|
|
def parsed_sents(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.parsed_sents(
|
|
self, self._resolve(fileids, categories)
|
|
)
|
|
|
|
def parsed_paras(self, fileids=None, categories=None):
|
|
return BracketParseCorpusReader.parsed_paras(
|
|
self, self._resolve(fileids, categories)
|
|
)
|
|
|
|
|
|
class AlpinoCorpusReader(BracketParseCorpusReader):
|
|
"""
|
|
Reader for the Alpino Dutch Treebank.
|
|
This corpus has a lexical breakdown structure embedded, as read by _parse
|
|
Unfortunately this puts punctuation and some other words out of the sentence
|
|
order in the xml element tree. This is no good for tag_ and word_
|
|
_tag and _word will be overridden to use a non-default new parameter 'ordered'
|
|
to the overridden _normalize function. The _parse function can then remain
|
|
untouched.
|
|
"""
|
|
|
|
def __init__(self, root, encoding="ISO-8859-1", tagset=None):
|
|
BracketParseCorpusReader.__init__(
|
|
self,
|
|
root,
|
|
"alpino\.xml",
|
|
detect_blocks="blankline",
|
|
encoding=encoding,
|
|
tagset=tagset,
|
|
)
|
|
|
|
def _normalize(self, t, ordered=False):
|
|
"""Normalize the xml sentence element in t.
|
|
The sentence elements <alpino_ds>, although embedded in a few overall
|
|
xml elements, are seperated by blank lines. That's how the reader can
|
|
deliver them one at a time.
|
|
Each sentence has a few category subnodes that are of no use to us.
|
|
The remaining word nodes may or may not appear in the proper order.
|
|
Each word node has attributes, among which:
|
|
- begin : the position of the word in the sentence
|
|
- pos : Part of Speech: the Tag
|
|
- word : the actual word
|
|
The return value is a string with all xml elementes replaced by
|
|
clauses: either a cat clause with nested clauses, or a word clause.
|
|
The order of the bracket clauses closely follows the xml.
|
|
If ordered == True, the word clauses include an order sequence number.
|
|
If ordered == False, the word clauses only have pos and word parts.
|
|
"""
|
|
if t[:10] != "<alpino_ds":
|
|
return ""
|
|
# convert XML to sexpr notation
|
|
t = re.sub(r' <node .*? cat="(\w+)".*>', r"(\1", t)
|
|
if ordered:
|
|
t = re.sub(
|
|
r' <node. *?begin="(\d+)".*? pos="(\w+)".*? word="([^"]+)".*?/>',
|
|
r"(\1 \2 \3)",
|
|
t,
|
|
)
|
|
else:
|
|
t = re.sub(r' <node .*?pos="(\w+)".*? word="([^"]+)".*?/>', r"(\1 \2)", t)
|
|
t = re.sub(r" </node>", r")", t)
|
|
t = re.sub(r"<sentence>.*</sentence>", r"", t)
|
|
t = re.sub(r"</?alpino_ds.*>", r"", t)
|
|
return t
|
|
|
|
def _tag(self, t, tagset=None):
|
|
tagged_sent = [
|
|
(int(o), w, p)
|
|
for (o, p, w) in SORTTAGWRD.findall(self._normalize(t, ordered=True))
|
|
]
|
|
tagged_sent.sort()
|
|
if tagset and tagset != self._tagset:
|
|
tagged_sent = [
|
|
(w, map_tag(self._tagset, tagset, p)) for (o, w, p) in tagged_sent
|
|
]
|
|
else:
|
|
tagged_sent = [(w, p) for (o, w, p) in tagged_sent]
|
|
return tagged_sent
|
|
|
|
def _word(self, t):
|
|
"""Return a correctly ordered list if words"""
|
|
tagged_sent = self._tag(t)
|
|
return [w for (w, p) in tagged_sent]
|