Installing NLTK 

pip install nltk
nltk.download()

Stop Words

Sometimes we need to filter out useless data to make the data more understandable by the computer. In natural language processing (NLP), such useless data (words) are called stop words.

from nltk.corpus import stopwords

print(set(stopwords.words('Arabic')))

print(set(stopwords.words('English')))

How can we remove the stop words from our own text? The example below shows how we can perform this task:

from nltk.tokenize import sent_tokenize,word_tokenize

from nltk.corpus import stopwords

data='All work and no play'


stopword=set(stopwords.words('English'))
word=word_tokenize(data)

wordsfilter=[]

for w in word:
    if w not in stopword:
        wordsfilter.append(w)
        
print(wordsfilter)

treebank

import nltk
nltk.download('treebank')
from nltk.corpus import treebank
t=treebank.parsed_sents('wsj_0001.mrg')[0]
t.draw()​

wordnet 

import nltk
from nltk.corpus import wordnet

syn=wordnet.synsets('NLP')

print(syn[0].definition())


synonyms=[]

for syn in wordnet.synsets('computer'):
    for lemma in syn.lemmas():
        synonyms.append(lemma.name())
print(synonyms)       

antonyms=[]
 
for syn in wordnet.synsets('small'):
    for l in syn.lemmas():
        if l.antonyms():
            antonyms.append(l.antonyms()[0].name())
print(antonyms)       

from nltk.stem import PorterStemmer
stemmer= PorterStemmer()
print(stemmer.stem('Working'))