在NLP任务中，常需要分析单词的词性，借助nltk库的pos_tag方法可以较好地实现。
以下是一个例子：
import nltk
line = 'i love this world which was beloved by all the people here'
tokens = nltk.word_tokenize(line)
# ['i', 'love', 'this', 'world', 'which', 'was', 'beloved', 'by',
# 'all', 'the', 'people', 'here']
pos_tags = nltk.pos_tag(tokens)
# [('i', 'RB'), ('love', 'VBP'), ('this', 'DT'), ('world', 'NN'), ('which', 'WDT'),
# ('was', 'VBD'), ('beloved', 'VBN'), ('by', 'IN'), ('all', 'PDT'), ('the', 'DT'),
# ('people', 'NNS'), ('here', 'RB')]
for word,pos in pos_tags:
if (pos == 'NN' or pos == 'NNP' or pos == 'NNS' or pos == 'NNPS'):
print word,pos
# world NN
# people NNS
作为nltk的替代，TextBlob库能够更进一步进行词组划分，例如“computer science”会被当做一个单词，而非"computer"和"science"
from textblob import TextBlob
txt = """Natural language processing (NLP) is a field of computer science, artificial intelligence, and computational linguistics concerned with the inter
actions between computers and human (natural) languages."""
blob = TextBlob(txt)
print(blob.noun_phrases)
# [u'natural language processing', 'nlp', u'computer science', u'artificial intelligence', u'computational linguistics']
更多例子请参考nltk官方教科书第五章
其中pos_tag分析出来的词性含义按照宾夕法尼亚大学tag词性对照表
| tag | 含义 |
|---|---|
| CC | Coordinating conjunction |
| CD | Cardinal number |
| DT | Determiner |
| EX | Existential there |
| FW | Foreign word |
| IN | Preposition or subordinating conjunction |
| JJ | Adjective |
| JJR | Adjective, comparative |
| JJS | Adjective, superlative |
| LS | List item marker |
| MD | Modal |
| NN | Noun, singular or mass |
| NNS | Noun, plural |
| NNP | Proper noun, singular |
| NNPS | Proper noun, plural |
| PDT | Predeterminer |
| POS | Possessive ending |
| PRP | Personal pronoun |
| PRP$ | Possessive pronoun |
| RB | Adverb |
| RBR | Adverb, comparative |
| RBS | Adverb, superlative |
| RP | Particle |
| SYM | Symbol |
| TO | to |
| UH | Interjection |
| VB | Verb, base form |
| VBD | Verb, past tense |
| VBG | Verb, gerund or present participle |
| VBN | Verb, past participle |
| VBP | Verb, non-3rd person singular present |
| VBZ | Verb, 3rd person singular present |
| WDT | Wh-determiner |
| WP | Wh-pronoun |
| WP$ | Possessive wh-pronoun |
| WRB | Wh-adverb |
