有什么好的、更好的或直接的方法可以从nltk树中得到分块结果吗?

不,NLTK中没有任何内置函数来返回特定深度的树。

How to Traverse an NLTK Tree object?

为了提高效率,您可以先迭代深度,并且仅当深度小于必要值时才重复,例如。

import nltk 
sentence = [("the", "DT"), ("little", "JJ"), ("yellow", "JJ"), ("dog", "NN"), ("barked","VBD"), ("at", "IN"), ("the", "DT"), ("cat", "NN")]

pattern = """NP: {<DT>?<JJ>*<NN>}
VBD: {<VBD>}
IN: {<IN>}"""
NPChunker = nltk.RegexpParser(pattern) 
result = NPChunker.parse(sentence)

def traverse_tree(tree, depth=float('inf')):
    """ 
    Traversing the Tree depth-first,
    yield leaves up to `depth` level.
    """
    for subtree in tree:
        if type(subtree) == nltk.tree.Tree:
            if subtree.height() <= depth:
                yield subtree.leaves()
                traverse_tree(subtree)


list(traverse_tree(result, 2))

[[('the', 'DT'), ('little', 'JJ'), ('yellow', 'JJ'), ('dog', 'NN')],
 [('barked', 'VBD')],
 [('at', 'IN')],
 [('the', 'DT'), ('cat', 'NN')]]

另一个例子:

x = """(S
  (NP the/DT 
      (AP little/JJ yellow/JJ)
       dog/NN)
  (VBD barked/VBD)
  (IN at/IN)
  (NP the/DT cat/NN))"""

list(traverse_tree(Tree.fromstring(x), 2))

[输出]:

[['barked/VBD'], ['at/IN'], ['the/DT', 'cat/NN']]