implementación de tf-idf python

#Importing required module
import numpy as np
from nltk.tokenize import  word_tokenize 
 
#Example text corpus for our tutorial
text = ['Topic sentences are similar to mini thesis statements.\
        Like a thesis statement, a topic sentence has a specific \
        main point. Whereas the thesis is the main point of the essay',\
        'the topic sentence is the main point of the paragraph.\
        Like the thesis statement, a topic sentence has a unifying function. \
        But a thesis statement or topic sentence alone doesn’t guarantee unity.', \
        'An essay is unified if all the paragraphs relate to the thesis,\
        whereas a paragraph is unified if all the sentences relate to the topic sentence.']
 
#Preprocessing the text data
sentences = []
word_set = []
 
for sent in text:
    x = [i.lower() for  i in word_tokenize(sent) if i.isalpha()]
    sentences.append(x)
    for word in x:
        if word not in word_set:
            word_set.append(word)
 
#Set of vocab 
word_set = set(word_set)
#Total documents in our corpus
total_documents = len(sentences)
 
#Creating an index for each word in our vocab.
index_dict = {} #Dictionary to store index for each word
i = 0
for word in word_set:
    index_dict[word] = i
    i += 1
Rias Dwi Prasasti