PorterStemmer doesn't seem to work

Question

I am new to python and practising with examples from book.
Can anyone explain why when I am trying to stem some example with this code nothing is changed?

>>> from nltk.stem import PorterStemmer
>>> stemmer=PorterStemmer()
>>> stemmer.stem('numpang wifi stop gadget shopping')
'numpang wifi stop gadget shopping'

But when I do this it works

>>> stemmer.stem('shopping')
'shop'

Answer 1

try this:

res = ",".join([ stemmer.stem(kw) for kw in 'numpang wifi stop gadget shopping'.split(" ")])

the problem is that, probably, that stemmer works on single words. your string has no "root" word, while the single word "shopping" has the root "shop". so you'll have to compute the stemming separately

edit:

from their source code ->

Stemming algorithms attempt to automatically remove suffixes (and in some
cases prefixes) in order to find the "root word" or stem of a given word. This
is useful in various natural language processing scenarios, such as search.

so i guess you are indeed forced to split your string by yourself

Answer 2

Try this:

from nltk.stem import PorterStemmer
from nltk.tokenize import word_tokenize

stemmer = PorterStemmer()

some_text = "numpang wifi stop gadget shopping"

words = word_tokenize(some_text)

for word in words:
    print(stemmer.stem(word))

Answer 3

Stemming is the process of reducing a given word to its base or inflected form, Here you are trying to stem entire sentence,

Follow these steps :

from nltk.tokenize import word_tokenize
from nltk.stem import PorterStemmer
sentence = "numpang wifi stop gadget shopping"
tokens = word_tokenize(sentence)
stemmer=PorterStemmer()

Output=[stemmer.stem(word) for word in tokens]