基于label分离NLTK子树

Question

I have a NLTK Parse tree, I want to separate Tree's leaves based on only the "S" labels. Note that, S should not overlap leaves.

Given the sentence "He won the Gusher Maraton, finishing in 30 minutes. "

The tree form from the corenlp is

tree = '(S
  (NP (PRP He))
  (VP
    (VBD won)
    (NP (DT the) (NNP Gusher) (NNP Marathon))
    (, ,)
    (S (VP (VBG finishing) (PP (IN in) (NP (CD 30) (NNS minutes))))))
  (. .))'

Idea is to extract 2 "S" and their leaves but not overlapping with each other. So the expected output should be "He won the Gusher Marathon,." and "finishing in 30 minutes."

# Tree manipulation

# Extract phrases from a parsed (chunked) tree
# Phrase = tag for the string phrase (sub-tree) to extract
# Returns: List of deep copies;  Recursive
def ExtractPhrases( myTree, phrase):
    myPhrases = []
    if (myTree.label() == phrase):
        myPhrases.append( myTree.copy(True) )
    for child in myTree:
        if (type(child) is Tree):
            list_of_phrases = ExtractPhrases(child, phrase)
            if (len(list_of_phrases) > 0):
                myPhrases.extend(list_of_phrases)
    return myPhrases

subtexts = set()
sep_tree = ExtractPhrases( Tree.fromstring(tree), 'S')
for sep in sep_tree:
    for subtree in sep.subtrees():
        if subtree.label()=="S":
            print(subtree)
            subtexts.add(' '.join(subtree.leaves()))
            #break

subtexts = list(subtexts)
print(subtexts)

I got the output

['He won the Gusher Marathon , finishing in 30 minutes .', 'finishing in 30 minutes']

I dont want to manipulate it in string level, rather tree level so expected output would be-

["He won the Gusher Marathon ,.",  "finishing in 30 minutes."]

Answer 1

This is my sample input:

a = 

'''

FREEDOM FROM RELIGION FOUNDATION

Darwin fish bumper stickers and assorted other atheist paraphernalia are
available from the Freedom From Religion Foundation in the US.

EVOLUTION DESIGNS

Evolution Designs sell the "Darwin fish".  It's a fish symbol, like the ones
Christians stick on their cars, but with feet and the word "Darwin" written
inside.  The deluxe moulded 3D plastic fish is $4.95 postpaid in the US.

'''


    sentences = nltk.sent_tokenize(a)
    sentences = [nltk.word_tokenize(sent) for sent in sentences]
    tagged_sentences = nltk.pos_tag_sents(sentences)
    chunked_sentences = list(nltk.ne_chunk_sents(tagged_sentences))

    for sent in chunked_sentences:
    for subtree in sent.subtrees(filter=lambda t: t.label()=='S'):
        print(subtree)

Here is my output:

(S
  (ORGANIZATION FREEDOM/NN)
  (ORGANIZATION FROM/NNP)
  RELIGION/NNP
  FOUNDATION/NNP
  Darwin/NNP
  fish/JJ
  bumper/NN
  stickers/NNS
  and/CC
  assorted/VBD
  other/JJ
  atheist/JJ
  paraphernalia/NNS
  are/VBP
  available/JJ
  from/IN
  the/DT
  (ORGANIZATION Freedom/NN From/NNP Religion/NNP Foundation/NNP)
  in/IN
  the/DT
  (GSP US/NNP)
  ./.)

(S
  (ORGANIZATION EVOLUTION/NNP)
  (ORGANIZATION DESIGNS/NNP Evolution/NNP)
  Designs/NNP
  sell/VB
  the/DT
  ``/``
  (PERSON Darwin/NNP)
  fish/NN
  ''/''
  ./.)

(S
  It/PRP
  's/VBZ
  a/DT
  fish/JJ
  symbol/NN
  ,/,
  like/IN
  the/DT
  ones/NNS
  Christians/NNPS
  stick/VBP
  on/IN
  their/PRP$
  cars/NNS
  ,/,
  but/CC
  with/IN
  feet/NNS
  and/CC
  the/DT
  word/NN
  ``/``
  (PERSON Darwin/NNP)
  ''/''
  written/VBN
  inside/RB
  ./.)

(S
  The/DT
  deluxe/NN
  moulded/VBD
  3D/CD
  plastic/JJ
  fish/NN
  is/VBZ
  $/$
  4.95/CD
  postpaid/NN
  in/IN
  the/DT
  (GSP US/NNP)
  ./.)