python - 如何在nltk python中通过标签获取树中的节点？

Question

我有一棵树:

(S  
    (WH-QUERY Which)  
    (FLIGHT-NP   
        (FLIGHT-CNP  
            (FLIGHT-CNP (FLIGHT-N flight))  
            (FLIGHT-DEST to (CITY-NP (CITY-NAME Hue) (CITY-N city)))))  
    (FLIGHT-VP  
        (FLIGHT-V arrives)  
        (FLIGHT-TIME (P-TIME at) (TIME-MOD 20:00HR))))  

我想通过 nltk 中的标签获取特定节点。例如，我有标签“CITY-NAME”，我想获取节点(CITY-NAM Hue)。我怎样才能实现这个目标？

Answer 1

一种方法是遍历树搜索匹配的节点:

for subtree in tree.subtrees():
     if subtree.label() == 'CITY-NAME':
          print subtree.leaves()