nltk's stopwords returns "TypeError: argument of type 'LazyCorpusLoader' is not iterable"
There are a couple of items that could be improved in your code:


nltk.corpus.stopwords is a nltk.corpus.util.LazyCorpusLoader. You might want stopwords.words('english'), a list of stop English words.
It can cause bugs to update a variable as you iterate through it, for example sentance in your code.
In your code preprocessed_reviews is not being updated.
You might want to tokenize instead of str.split().


Here is a revision version:

import nltk
from nltk.corpus import stopwords
from tqdm import tqdm

reviews_raw = ('The quick brown fox jumps over the lazy dog', "I have been doing what I should not been doing")
reviews_processed = []
for sentence in tqdm(reviews_raw):
    reviews_processed.append(' '.join(token.lower() for token in nltk.word_tokenize(sentence) if token.lower() not in stopwords.words('english')))

assert reviews_processed == ['quick brown fox jumps lazy dog', '']