pipeline/nltk/corpus/reader/bracket_parse.py

# Natural Language Toolkit: Penn Treebank Reader
#
# Copyright (C) 2001-2023 NLTK Project
# Author: Steven Bird <[email protected]>
#         Edward Loper <[email protected]>
# URL: <https://www.nltk.org/>
# For license information, see LICENSE.TXT
"""
Corpus reader for corpora that consist of parenthesis-delineated parse trees.
"""

import sys

from nltk.corpus.reader.api import *
from nltk.corpus.reader.util import *
from nltk.tag import map_tag
from nltk.tree import Tree

# 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.
        """
        SyntaxCorpusReader.__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 <[email protected]>
    """

    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 tagged_words(self, fileids=None, categories=None, tagset=None):
        return super().tagged_words(self._resolve(fileids, categories), tagset)

    def tagged_sents(self, fileids=None, categories=None, tagset=None):
        return super().tagged_sents(self._resolve(fileids, categories), tagset)

    def tagged_paras(self, fileids=None, categories=None, tagset=None):
        return super().tagged_paras(self._resolve(fileids, categories), tagset)

    def parsed_words(self, fileids=None, categories=None):
        return super().parsed_words(self._resolve(fileids, categories))

    def parsed_sents(self, fileids=None, categories=None):
        return super().parsed_sents(self._resolve(fileids, categories))

    def parsed_paras(self, fileids=None, categories=None):
        return super().parsed_paras(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,
            r"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 separated 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]