如何遍历树的所有节点? [英] How to iterate through all nodes of a tree?

问题描述

我想简化解析树的节点，即给定一个节点，我摆脱了第一个连字符以及该连字符之后的所有内容.例如，如果一个节点是NP-TMP-FG，我想使其成为NP，如果它是SBAR-SBJ，我希望使其成为SBAR，依此类推.这是我拥有的一个解析树的示例

I want to simplify my parse trees' nodes, i.e. given a node I get rid of the first hyphen and whatever that comes after that hyphen. For example if a node is NP-TMP-FG, I want to make it NP and if it is SBAR-SBJ, I want to make it SBAR and so on. This is an example of one parse tree that I have

( (S (S-TPC-2 (NP-SBJ (NP (DT The) (NN asbestos) (NN fiber) ) (, ,)
(NP (NN crocidolite) ) (, ,) ) (VP (VBZ is) (ADJP-PRD (RB unusually) (JJ resilient) )
(SBAR-TMP (IN once) (S (NP-SBJ (PRP it) ) (VP (VBZ enters) (NP (DT the) (NNS lungs) ))))
(, ,) (PP (IN with)(S-NOM (NP-SBJ (NP (RB even) (JJ brief) (NNS exposures) ) (PP (TO to)
(NP (PRP it) ))) (VP (VBG causing) (NP (NP (NNS symptoms) ) (SBAR (WHNP-1 (WDT that) )
(S (NP-SBJ (-NONE- *T*-1) ) (VP (VBP show) (PRT (RP up) ) (ADVP-TMP (NP (NNS decades) ) 
(JJ later) )))))))))) (, ,) (NP-SBJ (NNS researchers) ) (VP (VBD said)(SBAR (-NONE- 0) 
(S (-NONE- *T*-2) )))    (. .) )) 

这是我的代码，但是不起作用.

This is my code but it doesn't work.

import re
import nltk
from nltk.tree import *
tree = Tree.fromstring(line) // Each parse tree is stored in one single line
for subtree in tree.subtrees():
    re.sub('-.*', '', subtree.label())
print tree

我想问题是subtree.label()显示了节点，但是由于它是一个函数，因此无法更改. print subtree.label()的输出是:

I guess the problem is that subtree.label() shows the nodes but it cannot be changed since it is a function. The output of print subtree.label() is :

S
S-TPC-2
NP-SBJ
NP
DT
NN
,

以此类推...

推荐答案

我想到了这一点:

for subtree in tree.subtrees():
    s = subtree.label()
    subtree.set_label(re.sub('-.*', "", s))

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