📅 最后修改于: 2020-12-13 14:16:53 🧑 作者: Mango
在自然语言处理领域，我们遇到了两个或两个以上单词具有共同词根的情况。例如，三个词-同意，同意和同意具有相同的词根同意。涉及这些单词中任何一个的搜索应将它们视为相同的单词，即词根。因此，将所有单词链接到其根词变得至关重要。 NLTK库具有执行此链接并提供显示根词的输出的方法。
下面的程序使用Porter Stemming Algorithm进行词干分析。
import nltk
from nltk.stem.porter import PorterStemmer
porter_stemmer = PorterStemmer()
word_data = "It originated from the idea that there are readers who prefer learning new skills from the comforts of their drawing rooms"
# First Word tokenization
nltk_tokens = nltk.word_tokenize(word_data)
#Next find the roots of the word
for w in nltk_tokens:
print "Actual: %s Stem: %s" % (w,porter_stemmer.stem(w))
当我们执行上面的代码时，它产生以下结果。
Actual: It Stem: It
Actual: originated Stem: origin
Actual: from Stem: from
Actual: the Stem: the
Actual: idea Stem: idea
Actual: that Stem: that
Actual: there Stem: there
Actual: are Stem: are
Actual: readers Stem: reader
Actual: who Stem: who
Actual: prefer Stem: prefer
Actual: learning Stem: learn
Actual: new Stem: new
Actual: skills Stem: skill
Actual: from Stem: from
Actual: the Stem: the
Actual: comforts Stem: comfort
Actual: of Stem: of
Actual: their Stem: their
Actual: drawing Stem: draw
Actual: rooms Stem: room
词法化是类似词干的，但它为单词带来了上下文，因此将具有相似含义的单词与一个单词联系起来可以走得更远。例如，如果某个段落包含汽车，火车和汽车之类的词，则它将所有这些词链接到汽车。在下面的程序中，我们使用WordNet词汇数据库进行词素化。
import nltk
from nltk.stem import WordNetLemmatizer
wordnet_lemmatizer = WordNetLemmatizer()
word_data = "It originated from the idea that there are readers who prefer learning new skills from the comforts of their drawing rooms"
nltk_tokens = nltk.word_tokenize(word_data)
for w in nltk_tokens:
print "Actual: %s Lemma: %s" % (w,wordnet_lemmatizer.lemmatize(w))
当我们执行上面的代码时，它产生以下结果。
Actual: It Lemma: It
Actual: originated Lemma: originated
Actual: from Lemma: from
Actual: the Lemma: the
Actual: idea Lemma: idea
Actual: that Lemma: that
Actual: there Lemma: there
Actual: are Lemma: are
Actual: readers Lemma: reader
Actual: who Lemma: who
Actual: prefer Lemma: prefer
Actual: learning Lemma: learning
Actual: new Lemma: new
Actual: skills Lemma: skill
Actual: from Lemma: from
Actual: the Lemma: the
Actual: comforts Lemma: comfort
Actual: of Lemma: of
Actual: their Lemma: their
Actual: drawing Lemma: drawing
Actual: rooms Lemma: room