Why does my Flask chatbot code take a very long time to execute and does not respond at the 'app.run()' step?

Question

very long time consumed in executing the code and with no response

I've tried running the below code many times which is for creating a web application for a custom Q&A chatbot feeded by a custom data, but unfortunately the execution doesn't response every-time at the step of app.run()

import PyPDF2

def extract_text_from_pdf(file_path):
    text = ""
    with open(file_path, "rb") as file:
        reader = PyPDF2.PdfReader(file)
        for page in reader.pages:
            text += page.extract_text()
    return text
def chunk_text(text, chunk_size):
    chunks = []
    words = text.split()
    for i in range(0, len(words), chunk_size):
        chunk = " ".join(words[i:i+chunk_size])
        chunks.append(chunk)
    return chunks
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.metrics.pairwise import cosine_similarity
import numpy as np

def build_vector_store(chunks):
    vectorizer = TfidfVectorizer()
    vectors = vectorizer.fit_transform(chunks)
    vector_store = {
        "chunks": chunks,
        "vectorizer": vectorizer,
        "vectors": vectors.toarray()
    }
    return vector_store

def retrieve_most_similar_chunks(query, vector_store, top_k=5):
    query_vector = vector_store["vectorizer"].transform([query]).toarray()
    similarities = cosine_similarity(query_vector, vector_store["vectors"]).flatten()
    most_similar_indices = np.argpartition(similarities, -top_k)[-top_k:]
    return [vector_store["chunks"][i] for i in most_similar_indices]
def create_chatbot(pdf_file):
    text = extract_text_from_pdf(pdf_file)
  
    chunk_size = 500  # Adjust the chunk size as needed
    chunks = chunk_text(text, chunk_size)

    vector_store = build_vector_store(chunks)

    def chatbot(query):
        similar_chunks = retrieve_most_similar_chunks(query, vector_store)
        response = "I'm sorry, I couldn't find an answer to your question."
        if similar_chunks:
            response = "Here is some relevant information:\n\n"
            response += "\n\n".join(similar_chunks)
        return response

    return chatbot
from flask import Flask, request, jsonify

app = Flask(__name__)
chatbot = create_chatbot("/content/AP 107.pdf")  # Provide the PDF file path

@app.route("/api/chatbot", methods=["POST"])
def api_chatbot():
    data = request.get_json()
    query = data["query"]
    response = chatbot(query)
    return jsonify({"response": response})

if __name__ == "__main__":
    app.run()