用NLTK对POS标记词进行引理？

Question

我用nltk.POS_tag（）对一些单词进行了POS标记，因此它们被赋予了treebank标记。我想用已知的POS标签把这些词引申出来，但我不知道怎么做。我在看WordNetLemmatizer，但我不确定如何将树银行POS标签转换为lemmatizer接受的标签。如何简单地执行此转换，或者是否有使用树库标记的lemmatizer？

Answer 1

wordnet lemmatizer只知道四个词类（ADJ、ADV、NOUN和VERB），只有NOUN和VERB规则可以做任何特别有趣的事情。treebank标记集中的名词词组都以NN开头，动词标记都以VB开头，形容词标记以JJ开头，副词标记以RB开头。因此，从一组标签转换到另一组非常容易，比如：

from nltk.corpus import wordnet

morphy_tag = {'NN':wordnet.NOUN,'JJ':wordnet.ADJ,'VB':wordnet.VERB,'RB':wordnet.ADV}[penn_tag[:2]]

Answer 2

正如@engineercoding在对@rmalouf答案的评论中指出的那样，与WordNet相比，Treebank中有更多的标记，请参见here for details。

以下映射覆盖尽可能多的基，它还显式地定义了在WordNet中没有匹配项的POS标记：

# Create a map between Treebank and WordNet 
from nltk.corpus import wordnet as wn

# WordNet POS tags are: NOUN = 'n', ADJ = 's', VERB = 'v', ADV = 'r', ADJ_SAT = 'a'
# Descriptions (c) https://web.stanford.edu/~jurafsky/slp3/10.pdf
tag_map = {
        'CC':None, # coordin. conjunction (and, but, or)  
        'CD':wn.NOUN, # cardinal number (one, two)             
        'DT':None, # determiner (a, the)                    
        'EX':wn.ADV, # existential ‘there’ (there)           
        'FW':None, # foreign word (mea culpa)             
        'IN':wn.ADV, # preposition/sub-conj (of, in, by)   
        'JJ':[wn.ADJ, wn.ADJ_SAT], # adjective (yellow)                  
        'JJR':[wn.ADJ, wn.ADJ_SAT], # adj., comparative (bigger)          
        'JJS':[wn.ADJ, wn.ADJ_SAT], # adj., superlative (wildest)           
        'LS':None, # list item marker (1, 2, One)          
        'MD':None, # modal (can, should)                    
        'NN':wn.NOUN, # noun, sing. or mass (llama)          
        'NNS':wn.NOUN, # noun, plural (llamas)                  
        'NNP':wn.NOUN, # proper noun, sing. (IBM)              
        'NNPS':wn.NOUN, # proper noun, plural (Carolinas)
        'PDT':[wn.ADJ, wn.ADJ_SAT], # predeterminer (all, both)            
        'POS':None, # possessive ending (’s )               
        'PRP':None, # personal pronoun (I, you, he)     
        'PRP$':None, # possessive pronoun (your, one’s)    
        'RB':wn.ADV, # adverb (quickly, never)            
        'RBR':wn.ADV, # adverb, comparative (faster)        
        'RBS':wn.ADV, # adverb, superlative (fastest)     
        'RP':[wn.ADJ, wn.ADJ_SAT], # particle (up, off)
        'SYM':None, # symbol (+,%, &)
        'TO':None, # “to” (to)
        'UH':None, # interjection (ah, oops)
        'VB':wn.VERB, # verb base form (eat)
        'VBD':wn.VERB, # verb past tense (ate)
        'VBG':wn.VERB, # verb gerund (eating)
        'VBN':wn.VERB, # verb past participle (eaten)
        'VBP':wn.VERB, # verb non-3sg pres (eat)
        'VBZ':wn.VERB, # verb 3sg pres (eats)
        'WDT':None, # wh-determiner (which, that)
        'WP':None, # wh-pronoun (what, who)
        'WP$':None, # possessive (wh- whose)
        'WRB':None, # wh-adverb (how, where)
        '$':None, #  dollar sign ($)
        '#':None, # pound sign (#)
        '“':None, # left quote (‘ or “)
        '”':None, # right quote (’ or ”)
        '(':None, # left parenthesis ([, (, {, <)
        ')':None, # right parenthesis (], ), }, >)
        ',':None, # comma (,)
        '.':None, # sentence-final punc (. ! ?)
        ':':None # mid-sentence punc (: ; ... – -)
    }