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298 lines
11 KiB
Python
298 lines
11 KiB
Python
# Natural Language Toolkit: SemCor Corpus Reader
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#
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# Copyright (C) 2001-2019 NLTK Project
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# Author: Nathan Schneider <nschneid@cs.cmu.edu>
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# URL: <http://nltk.org/>
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# For license information, see LICENSE.TXT
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"""
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Corpus reader for the SemCor Corpus.
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"""
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from __future__ import absolute_import, unicode_literals
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__docformat__ = 'epytext en'
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from nltk.corpus.reader.api import *
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from nltk.corpus.reader.xmldocs import XMLCorpusReader, XMLCorpusView
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from nltk.tree import Tree
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class SemcorCorpusReader(XMLCorpusReader):
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"""
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Corpus reader for the SemCor Corpus.
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For access to the complete XML data structure, use the ``xml()``
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method. For access to simple word lists and tagged word lists, use
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``words()``, ``sents()``, ``tagged_words()``, and ``tagged_sents()``.
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"""
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def __init__(self, root, fileids, wordnet, lazy=True):
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XMLCorpusReader.__init__(self, root, fileids)
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self._lazy = lazy
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self._wordnet = wordnet
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def words(self, fileids=None):
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"""
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:return: the given file(s) as a list of words and punctuation symbols.
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:rtype: list(str)
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"""
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return self._items(fileids, 'word', False, False, False)
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def chunks(self, fileids=None):
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"""
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:return: the given file(s) as a list of chunks,
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each of which is a list of words and punctuation symbols
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that form a unit.
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:rtype: list(list(str))
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"""
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return self._items(fileids, 'chunk', False, False, False)
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def tagged_chunks(self, fileids=None, tag=('pos' or 'sem' or 'both')):
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"""
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:return: the given file(s) as a list of tagged chunks, represented
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in tree form.
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:rtype: list(Tree)
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:param tag: `'pos'` (part of speech), `'sem'` (semantic), or `'both'`
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to indicate the kind of tags to include. Semantic tags consist of
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WordNet lemma IDs, plus an `'NE'` node if the chunk is a named entity
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without a specific entry in WordNet. (Named entities of type 'other'
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have no lemma. Other chunks not in WordNet have no semantic tag.
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Punctuation tokens have `None` for their part of speech tag.)
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"""
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return self._items(fileids, 'chunk', False, tag != 'sem', tag != 'pos')
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def sents(self, fileids=None):
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"""
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:return: the given file(s) as a list of sentences, each encoded
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as a list of word strings.
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:rtype: list(list(str))
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"""
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return self._items(fileids, 'word', True, False, False)
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def chunk_sents(self, fileids=None):
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"""
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:return: the given file(s) as a list of sentences, each encoded
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as a list of chunks.
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:rtype: list(list(list(str)))
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"""
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return self._items(fileids, 'chunk', True, False, False)
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def tagged_sents(self, fileids=None, tag=('pos' or 'sem' or 'both')):
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"""
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:return: the given file(s) as a list of sentences. Each sentence
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is represented as a list of tagged chunks (in tree form).
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:rtype: list(list(Tree))
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:param tag: `'pos'` (part of speech), `'sem'` (semantic), or `'both'`
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to indicate the kind of tags to include. Semantic tags consist of
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WordNet lemma IDs, plus an `'NE'` node if the chunk is a named entity
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without a specific entry in WordNet. (Named entities of type 'other'
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have no lemma. Other chunks not in WordNet have no semantic tag.
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Punctuation tokens have `None` for their part of speech tag.)
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"""
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return self._items(fileids, 'chunk', True, tag != 'sem', tag != 'pos')
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def _items(self, fileids, unit, bracket_sent, pos_tag, sem_tag):
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if unit == 'word' and not bracket_sent:
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# the result of the SemcorWordView may be a multiword unit, so the
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# LazyConcatenation will make sure the sentence is flattened
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_ = lambda *args: LazyConcatenation(
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(SemcorWordView if self._lazy else self._words)(*args)
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)
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else:
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_ = SemcorWordView if self._lazy else self._words
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return concat(
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[
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_(fileid, unit, bracket_sent, pos_tag, sem_tag, self._wordnet)
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for fileid in self.abspaths(fileids)
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]
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)
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def _words(self, fileid, unit, bracket_sent, pos_tag, sem_tag):
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"""
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Helper used to implement the view methods -- returns a list of
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tokens, (segmented) words, chunks, or sentences. The tokens
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and chunks may optionally be tagged (with POS and sense
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information).
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:param fileid: The name of the underlying file.
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:param unit: One of `'token'`, `'word'`, or `'chunk'`.
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:param bracket_sent: If true, include sentence bracketing.
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:param pos_tag: Whether to include part-of-speech tags.
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:param sem_tag: Whether to include semantic tags, namely WordNet lemma
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and OOV named entity status.
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"""
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assert unit in ('token', 'word', 'chunk')
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result = []
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xmldoc = ElementTree.parse(fileid).getroot()
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for xmlsent in xmldoc.findall('.//s'):
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sent = []
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for xmlword in _all_xmlwords_in(xmlsent):
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itm = SemcorCorpusReader._word(
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xmlword, unit, pos_tag, sem_tag, self._wordnet
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)
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if unit == 'word':
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sent.extend(itm)
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else:
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sent.append(itm)
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if bracket_sent:
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result.append(SemcorSentence(xmlsent.attrib['snum'], sent))
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else:
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result.extend(sent)
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assert None not in result
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return result
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@staticmethod
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def _word(xmlword, unit, pos_tag, sem_tag, wordnet):
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tkn = xmlword.text
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if not tkn:
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tkn = "" # fixes issue 337?
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lemma = xmlword.get('lemma', tkn) # lemma or NE class
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lexsn = xmlword.get('lexsn') # lex_sense (locator for the lemma's sense)
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if lexsn is not None:
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sense_key = lemma + '%' + lexsn
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wnpos = ('n', 'v', 'a', 'r', 's')[
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int(lexsn.split(':')[0]) - 1
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] # see http://wordnet.princeton.edu/man/senseidx.5WN.html
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else:
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sense_key = wnpos = None
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redef = xmlword.get(
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'rdf', tkn
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) # redefinition--this indicates the lookup string
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# does not exactly match the enclosed string, e.g. due to typographical adjustments
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# or discontinuity of a multiword expression. If a redefinition has occurred,
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# the "rdf" attribute holds its inflected form and "lemma" holds its lemma.
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# For NEs, "rdf", "lemma", and "pn" all hold the same value (the NE class).
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sensenum = xmlword.get('wnsn') # WordNet sense number
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isOOVEntity = 'pn' in xmlword.keys() # a "personal name" (NE) not in WordNet
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pos = xmlword.get(
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'pos'
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) # part of speech for the whole chunk (None for punctuation)
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if unit == 'token':
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if not pos_tag and not sem_tag:
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itm = tkn
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else:
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itm = (
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(tkn,)
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+ ((pos,) if pos_tag else ())
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+ ((lemma, wnpos, sensenum, isOOVEntity) if sem_tag else ())
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)
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return itm
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else:
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ww = tkn.split('_') # TODO: case where punctuation intervenes in MWE
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if unit == 'word':
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return ww
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else:
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if sensenum is not None:
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try:
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sense = wordnet.lemma_from_key(sense_key) # Lemma object
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except Exception:
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# cannot retrieve the wordnet.Lemma object. possible reasons:
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# (a) the wordnet corpus is not downloaded;
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# (b) a nonexistant sense is annotated: e.g., such.s.00 triggers:
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# nltk.corpus.reader.wordnet.WordNetError: No synset found for key u'such%5:00:01:specified:00'
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# solution: just use the lemma name as a string
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try:
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sense = '%s.%s.%02d' % (
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lemma,
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wnpos,
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int(sensenum),
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) # e.g.: reach.v.02
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except ValueError:
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sense = (
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lemma + '.' + wnpos + '.' + sensenum
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) # e.g. the sense number may be "2;1"
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bottom = [Tree(pos, ww)] if pos_tag else ww
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if sem_tag and isOOVEntity:
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if sensenum is not None:
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return Tree(sense, [Tree('NE', bottom)])
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else: # 'other' NE
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return Tree('NE', bottom)
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elif sem_tag and sensenum is not None:
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return Tree(sense, bottom)
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elif pos_tag:
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return bottom[0]
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else:
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return bottom # chunk as a list
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def _all_xmlwords_in(elt, result=None):
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if result is None:
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result = []
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for child in elt:
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if child.tag in ('wf', 'punc'):
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result.append(child)
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else:
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_all_xmlwords_in(child, result)
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return result
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class SemcorSentence(list):
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"""
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A list of words, augmented by an attribute ``num`` used to record
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the sentence identifier (the ``n`` attribute from the XML).
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"""
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def __init__(self, num, items):
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self.num = num
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list.__init__(self, items)
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class SemcorWordView(XMLCorpusView):
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"""
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A stream backed corpus view specialized for use with the BNC corpus.
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"""
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def __init__(self, fileid, unit, bracket_sent, pos_tag, sem_tag, wordnet):
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"""
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:param fileid: The name of the underlying file.
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:param unit: One of `'token'`, `'word'`, or `'chunk'`.
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:param bracket_sent: If true, include sentence bracketing.
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:param pos_tag: Whether to include part-of-speech tags.
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:param sem_tag: Whether to include semantic tags, namely WordNet lemma
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and OOV named entity status.
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"""
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if bracket_sent:
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tagspec = '.*/s'
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else:
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tagspec = '.*/s/(punc|wf)'
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self._unit = unit
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self._sent = bracket_sent
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self._pos_tag = pos_tag
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self._sem_tag = sem_tag
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self._wordnet = wordnet
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XMLCorpusView.__init__(self, fileid, tagspec)
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def handle_elt(self, elt, context):
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if self._sent:
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return self.handle_sent(elt)
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else:
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return self.handle_word(elt)
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def handle_word(self, elt):
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return SemcorCorpusReader._word(
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elt, self._unit, self._pos_tag, self._sem_tag, self._wordnet
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)
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def handle_sent(self, elt):
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sent = []
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for child in elt:
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if child.tag in ('wf', 'punc'):
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itm = self.handle_word(child)
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if self._unit == 'word':
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sent.extend(itm)
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else:
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sent.append(itm)
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else:
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raise ValueError('Unexpected element %s' % child.tag)
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return SemcorSentence(elt.attrib['snum'], sent)
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