86 lines
3.0 KiB
Python
86 lines
3.0 KiB
Python
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from typing import Iterator, Tuple, Union
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from ...errors import Errors
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from ...symbols import NOUN, PRON, PROPN
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from ...tokens import Doc, Span
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def noun_chunks(doclike: Union[Doc, Span]) -> Iterator[Tuple[int, int, int]]:
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"""
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Detect base noun phrases from a dependency parse. Works on both Doc and Span.
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"""
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labels = [
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"nsubj",
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"nsubj:pass",
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"obj",
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"obl",
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"obl:agent",
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"nmod",
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"pcomp",
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"appos",
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"ROOT",
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]
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post_modifiers = ["flat", "flat:name", "fixed", "compound"]
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doc = doclike.doc # Ensure works on both Doc and Span.
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if not doc.has_annotation("DEP"):
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raise ValueError(Errors.E029)
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np_deps = {doc.vocab.strings.add(label) for label in labels}
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np_modifs = {doc.vocab.strings.add(modifier) for modifier in post_modifiers}
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np_label = doc.vocab.strings.add("NP")
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adj_label = doc.vocab.strings.add("amod")
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det_label = doc.vocab.strings.add("det")
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det_pos = doc.vocab.strings.add("DET")
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adp_label = doc.vocab.strings.add("ADP")
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conj = doc.vocab.strings.add("conj")
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conj_pos = doc.vocab.strings.add("CCONJ")
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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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right_childs = list(word.rights)
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right_child = right_childs[0] if right_childs else None
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if right_child:
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if (
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right_child.dep == adj_label
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): # allow chain of adjectives by expanding to right
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right_end = right_child.right_edge
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elif (
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right_child.dep == det_label and right_child.pos == det_pos
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): # cut relative pronouns here
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right_end = right_child
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elif right_child.dep in np_modifs: # Check if we can expand to right
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right_end = word.right_edge
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else:
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right_end = word
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else:
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right_end = word
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prev_end = right_end.i
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left_index = word.left_edge.i
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left_index = (
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left_index + 1 if word.left_edge.pos == adp_label else left_index
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)
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yield left_index, right_end.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.i
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left_index = word.left_edge.i # eliminate left attached conjunction
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left_index = (
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left_index + 1 if word.left_edge.pos == conj_pos else left_index
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)
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yield left_index, word.i + 1, np_label
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SYNTAX_ITERATORS = {"noun_chunks": noun_chunks}
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