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40 lines
1.5 KiB
Python
40 lines
1.5 KiB
Python
from typing import Union, Iterator
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from ...symbols import NOUN, PROPN, PRON
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from ...errors import Errors
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from ...tokens import Doc, Span
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def noun_chunks(doclike: Union[Doc, Span]) -> Iterator[Span]:
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"""Detect base noun phrases from a dependency parse. Works on Doc and Span."""
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# fmt: off
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labels = ["nsubj", "nsubj:pass", "obj", "iobj", "ROOT", "appos", "nmod", "nmod:poss"]
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# fmt: on
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doc = doclike.doc # Ensure works on both Doc and Span.
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if not doc.is_parsed:
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raise ValueError(Errors.E029)
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np_deps = [doc.vocab.strings[label] for label in labels]
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conj = doc.vocab.strings.add("conj")
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np_label = doc.vocab.strings.add("NP")
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prev_end = -1
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for i, word in enumerate(doclike):
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if word.pos not in (NOUN, PROPN, PRON):
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continue
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# Prevent nested chunks from being produced
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if word.left_edge.i <= prev_end:
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continue
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if word.dep in np_deps:
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prev_end = word.right_edge.i
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yield word.left_edge.i, word.right_edge.i + 1, np_label
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elif word.dep == conj:
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head = word.head
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while head.dep == conj and head.head.i < head.i:
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head = head.head
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# If the head is an NP, and we're coordinated to it, we're an NP
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if head.dep in np_deps:
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prev_end = word.right_edge.i
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yield word.left_edge.i, word.right_edge.i + 1, np_label
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SYNTAX_ITERATORS = {"noun_chunks": noun_chunks}
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