python - Following StackAbuse guide but it isn't working

Question

I am following this guide on a rnn text generating network using tensorflow and numpy. I have been following the guide almost word for word but it has encountered an error on 23 and 26 due to a "TypeError: can only join an interable". I'm not sure what that could mean as I have been pretty much copying the guide. Anyone have an idea as to what the problem could be? code:

import numpy
import sys
from nltk.tokenize import RegexpTokenizer
from nltk.corpus import stopwords
from keras.models import Sequential
from keras.layers import Dense, Dropout, LSTM
from keras.utils import np_utils
from keras.callbacks import ModelCheckpoint

file = open("C:/Users/alpha/Desktop/coding/pickles.txt").read()


def tokenizeWords(input):
    # lowercase everything to standardize
    input = input.lower()

    # instantiate the tokenizer
    tokenizer = RegexpTokenizer(r'w+')
    tokens = tokenizer.tokenize(input)

    # if the created token isn't in the stop words, make it part of "filtered"
    filtered = filter(lambda token: token not in stopwords.words('english'), tokens)
    return "".join(filter)


processed_inputs = tokenizeWords(file)

chars = sorted(list(set(processed_inputs)))
char_to_num = dict((c, i) for i, c in enumerate(chars))
input_len = len(processed_inputs)
vocab_len = len(chars)
print("Total number of characters", input_len)
print("Total vocab", vocab_len)

Answer 1

The error says that join() method requires an iterable such as list etc. but you are passing filter() method, which is incorrect. The line

return "".join(filter)

is incorrect. You want to use the filtered list and not the filter method

return "".join(filtered)