Ensure noun chunks can't be nested. Closes
@@ -10,15 +10,22 @@ def english_noun_chunks(obj):
Works on both Doc and Span.
"""
labels = ['nsubj', 'dobj', 'nsubjpass', 'pcomp', 'pobj',
- 'attr', 'ROOT', 'root']
+ 'attr', 'ROOT']
doc = obj.doc # Ensure works on both Doc and Span.
np_deps = [doc.vocab.strings[label] for label in labels]
conj = doc.vocab.strings['conj']
np_label = doc.vocab.strings['NP']
+ seen = set()
for i, word in enumerate(obj):
if word.pos not in (NOUN, PROPN, PRON):
continue
+ # Prevent nested chunks from being produced
+ if word.i in seen:
+ continue
if word.dep in np_deps:
+ if any(w.i in seen for w in word.subtree):
+ continue
+ seen.update(j for j in range(word.left_edge.i, word.i+1))
yield word.left_edge.i, word.i+1, np_label
elif word.dep == conj:
head = word.head
@@ -26,6 +33,9 @@ def english_noun_chunks(obj):
head = head.head
# If the head is an NP, and we're coordinated to it, we're an NP
if head.dep in np_deps:
+ if any(w.i in seen for w in word.subtree):
+ continue
+ seen.update(j for j in range(word.left_edge.i, word.i+1))
yield word.left_edge.i, word.i+1, np_label
