How to extend the stopword list from NLTK and remove stop words with the extended list?

Question

I have tried two ways of removing stopwords, both of which I run into issues:

Method 1:

cachedStopWords = stopwords.words("english")
words_to_remove = """with some your just have from it's /via & that they your there this into providing would can't"""
remove = tu.removal_set(words_to_remove, query)
remove2 = tu.removal_set(cachedStopWords, query)

In this case, only the first remove function works. remove2 doesn't work.

Method 2:

lines = tu.lines_cleanup([sentence for sentence in sentence_list], remove=remove)
words = '\n'.join(lines).split()
print words # list of words

output looks like this ["Hello", "Good", "day"]

I try to remove stopwords from words. This is my code:

for word in words:
    if word in cachedStopwords:
        continue
    else:
        new_words='\n'.join(word)

print new_words

The output looks like this:

H
e
l
l
o

Cant figure out what is wrong with the above 2 methods. Please advice.

Answer 1

Use this for increasing the stopword list :

from nltk.corpus import stopwords
stop_words = stopwords.words('english')
print(len(stop_words))
stop_words.extend(['from', 'subject', 're', 'edu', 'use'])
print(len(stop_words))

Output:

179

184

Answer 2

I think what you want to achieve is to extend the list of stopwords from NLTK. Since the stopwords in NLTK are kept in a single list, you can simply do this:

>>> from nltk.corpus import stopwords
>>> stoplist = stopwords.words('english')
>>> stoplist
[u'i', u'me', u'my', u'myself', u'we', u'our', u'ours', u'ourselves', u'you', u'your', u'yours', u'yourself', u'yourselves', u'he', u'him', u'his', u'himself', u'she', u'her', u'hers', u'herself', u'it', u'its', u'itself', u'they', u'them', u'their', u'theirs', u'themselves', u'what', u'which', u'who', u'whom', u'this', u'that', u'these', u'those', u'am', u'is', u'are', u'was', u'were', u'be', u'been', u'being', u'have', u'has', u'had', u'having', u'do', u'does', u'did', u'doing', u'a', u'an', u'the', u'and', u'but', u'if', u'or', u'because', u'as', u'until', u'while', u'of', u'at', u'by', u'for', u'with', u'about', u'against', u'between', u'into', u'through', u'during', u'before', u'after', u'above', u'below', u'to', u'from', u'up', u'down', u'in', u'out', u'on', u'off', u'over', u'under', u'again', u'further', u'then', u'once', u'here', u'there', u'when', u'where', u'why', u'how', u'all', u'any', u'both', u'each', u'few', u'more', u'most', u'other', u'some', u'such', u'no', u'nor', u'not', u'only', u'own', u'same', u'so', u'than', u'too', u'very', u's', u't', u'can', u'will', u'just', u'don', u'should', u'now']
>>> more_stopwords = """with some your just have from it's /via & that they your there this into providing would can't"""
>>> stoplist += more_stopwords.split()
>>> sent = "With some of hacks to your line of code , we can simply extract the data you need ."
>>> sent_with_no_stopwords = [word for word in sent.split() if word not in stoplist]
>>> sent_with_no_stopwords
['With', 'hacks', 'line', 'code', ',', 'simply', 'extract', 'data', 'need', '.']
# Note that the "With" is different from "with".
# So let's try this:
>>> sent_with_no_stopwords = [word for word in sent.lower().split() if word not in stoplist]
>>> sent_with_no_stopwords
['hacks', 'line', 'code', ',', 'simply', 'extract', 'data', 'need', '.']
# To get it back into a string:
>>> new_sent = " ".join(sent_with_no_stopwords)
>>> new_sent
'hacks line code , simply extract data need .'