How to make a whatsapp chatbot in python

import numpy as np

import nltk

import string

import random

f=open('chatbot.txt','r',errors='ignore')

raw_doc=f.read()

raw_doc=raw_doc.lower()

nltk.download('punkt')

nltk.download('wordnet')

sent_tokens=nltk.sent_tokenize(raw_doc)

word_tokens=nltk.word_tokenize(raw_doc)

sent_tokens[:2]

word_tokens[:2]

lemmer=nltk.stem.WordNetLemmatizer()

def LemTokens(tokens):

    return[lemmer.lemmatize(token)for token in tokens]

remove_punct_dict= dict((ord(punct),None) for punct in string.punctuation)

def LemNormalize(text):

    return LemTokens(nltk.word_tokenize(text.lower().translate(remove_punct_dict))) 

GREET_INPUTS=("hello","hi","sup","greetings","what's up","hey",)

GREET_RESPONSES=("hi","hey","*nods*","hi there","hello","I'm glad! You are talking to me")

def greet(sentence):

    for word in sentence.split():

        if word.lower() in GREET_INPUTS:

            return random.choice(GREET_RESPONSES)

from sklearn.feature_extraction.text import TfidfVectorizer

from sklearn.metrics.pairwise import cosine_similarity

def response(user_response):

  robo1_response=''

  TfidfVec=TfidfVectorizer(tokenizer=LemNormalize, stop_words='english')

  tfidf=TfidfVec.fit_transform(sent_tokens)

  vals=cosine_similarity(tfidf[-1],tfidf)

  idx=vals.argsort()[0][-2]

  flat=vals.flatten()

  flat.sort()

  req_tfidf=flat[-2]

  if(req_tfidf==0):

    robo1_response=robo1_response+"I am sorry! I don't understand you"

    return robo1_response

  else:

    robo1_response=robo1_response+sent_tokens[idx]

    return robo1_response

flag=True

print("Bot: My name is Stark. Let's have a conversation! Also, if you want to exit anytime, just type Bye!")

while(flag==True):

    user_response=input()

    user_response=user_response.lower()

    if (user_response!='bye'):

         if (user_response=='thanks' or user_response=='thank you'):

              flag=False

              print("BOT: You are welcome..")

         else:

            if(greet(user_response)!=None):

              print("BOT: "+greet(user_response))

            else:

              sent_tokens.append(user_response)

              word_tokens=word_tokens+nltk.word_tokenize(user_response)

              final_words=list(set(word_tokens))

              print("BOT: ",end="")

              print(response(user_response))

              sent_tokens.remove(user_response)

    else:

        flag=False

        print("BOT: Goodbye! Take care <3")

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