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"""
Triples
-------
:mod:`textacy.extract.triples`: Extract structured triples from a document or sentence
through rule-based pattern-matching of the annotated tokens.
"""
from __future__ import annotations
import collections
from operator import attrgetter
from typing import Iterable, List, Tuple
from spacy.symbols import (
AUX, VERB,
agent, attr, aux, auxpass, csubj, csubjpass, dobj, neg, nsubj, nsubjpass, obj, pobj, xcomp,
)
from spacy.tokens import Span, Token
from textacy import types
_NOMINAL_SUBJ_DEPS = {nsubj, nsubjpass}
_CLAUSAL_SUBJ_DEPS = {csubj, csubjpass}
_ACTIVE_SUBJ_DEPS = {csubj, nsubj}
_VERB_MODIFIER_DEPS = {aux, auxpass, neg}
SVOTriple: Tuple[List[Token], List[Token], List[Token]] = collections.namedtuple(
"SVOTriple", ["subject", "verb", "object"]
)
def subject_verb_object_triples(doclike: types.DocLike) -> Iterable[SVOTriple]:
"""
Extract an ordered sequence of subject-verb-object triples from a document
or sentence.
Args:
doclike
Yields:
Next SVO triple as (subject, verb, object), in approximate order of appearance.
"""
if isinstance(doclike, Span):
sents = [doclike]
else:
sents = doclike.sents
for sent in sents:
# connect subjects/objects to direct verb heads
# and expand them to include conjuncts, compound nouns, ...
verb_sos = collections.defaultdict(lambda: collections.defaultdict(set))
for tok in sent:
head = tok.head
# ensure entry for all verbs, even if empty
# to catch conjugate verbs without direct subject/object deps
if tok.pos == VERB:
_ = verb_sos[tok]
# nominal subject of active or passive verb
if tok.dep in _NOMINAL_SUBJ_DEPS:
if head.pos == VERB:
verb_sos[head]["subjects"].update(expand_noun(tok))
# clausal subject of active or passive verb
elif tok.dep in _CLAUSAL_SUBJ_DEPS:
if head.pos == VERB:
verb_sos[head]["subjects"].update(tok.subtree)
# nominal direct object of transitive verb
elif tok.dep == obj:
if head.pos == VERB:
verb_sos[head]["objects"].update(expand_noun(tok))
# prepositional object acting as agent of passive verb
elif tok.dep == pobj:
if head.dep == agent and head.head.pos == VERB:
verb_sos[head.head]["objects"].update(expand_noun(tok))
# open clausal complement, but not as a secondary predicate
elif tok.dep == xcomp:
if (
head.pos == VERB
and not any(child.dep == obj for child in head.children)
):
# TODO: just the verb, or the whole tree?
# verb_sos[verb]["objects"].update(expand_verb(tok))
verb_sos[head]["objects"].update(tok.subtree)
# fill in any indirect relationships connected via verb conjuncts
for verb, so_dict in verb_sos.items():
conjuncts = verb.conjuncts
if so_dict.get("subjects"):
for conj in conjuncts:
conj_so_dict = verb_sos.get(conj)
if conj_so_dict and not conj_so_dict.get("subjects"):
conj_so_dict["subjects"].update(so_dict["subjects"])
if not so_dict.get("objects"):
so_dict["objects"].update(
obj
for conj in conjuncts
for obj in verb_sos.get(conj, {}).get("objects", [])
)
# expand verbs and restructure into svo triples
for verb, so_dict in verb_sos.items():
if so_dict["subjects"] and so_dict["objects"]:
yield SVOTriple(
subject=sorted(so_dict["subjects"], key=attrgetter("i")),
verb=sorted(expand_verb(verb), key=attrgetter("i")),
object=sorted(so_dict["objects"], key=attrgetter("i")),
)
def expand_noun(tok: Token) -> List[Token]:
"""Expand a noun token to include all associated conjunct and compound nouns."""
tok_and_conjuncts = [tok] + list(tok.conjuncts)
compounds = [
child
for tc in tok_and_conjuncts
for child in tc.children
# TODO: why doesn't compound import from spacy.symbols?
if child.dep_ == "compound"
]
return tok_and_conjuncts + compounds
def expand_verb(tok: Token) -> List[Token]:
"""Expand a verb token to include all associated auxiliary and negation tokens."""
verb_modifiers = [
child for child in tok.children if child.dep in _VERB_MODIFIER_DEPS
]
return [tok] + verb_modifiers
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