Where can I write server code for stripe payment in Django project?

Question

I am working on React JS to implement stripe payment gateway. I am using Django as a backend Server. In stripe documentation. https://stripe.com/docs/checkout/integration-builder?server=python

there is following code given for implementation

code for react App.js

import React, { useState, useEffect } from "react";
import "./App.css";

const ProductDisplay = () => (
  <section>
    <div className="product">
      <img
        src="https://i.imgur.com/EHyR2nP.png"
        alt="The cover of Stubborn Attachments"
      />
      <div className="description">
      <h3>Stubborn Attachments</h3>
      <h5>$20.00</h5>
      </div>
    </div>
    <form action="/create-checkout-session" method="POST">
      <button type="submit">
        Checkout
      </button>
    </form>
  </section>
);

const Message = ({ message }) => (
  <section>
    <p>{message}</p>
  </section>
);

export default function App() {
  const [message, setMessage] = useState("");

  useEffect(() => {
    // Check to see if this is a redirect back from Checkout
    const query = new URLSearchParams(window.location.search);

    if (query.get("success")) {
      setMessage("Order placed! You will receive an email confirmation.");
    }

    if (query.get("canceled")) {
      setMessage(
        "Order canceled -- continue to shop around and checkout when you're ready."
      );
    }
  }, []);

  return message ? (
    <Message message={message} />
  ) : (
    <ProductDisplay />
  );
}

code for python server.py

"""
server.py
Stripe Sample.
Python 3.6 or newer required.
"""
import os
from flask import Flask, redirect, request

import stripe
# This is your real test secret API key.
stripe.api_key = 'my key'

app = Flask(__name__,
            static_url_path='',
            static_folder='public')

YOUR_DOMAIN = 'http://localhost:3000/checkout'

@app.route('/create-checkout-session', methods=['POST'])
def create_checkout_session():
    try:
        checkout_session = stripe.checkout.Session.create(
            line_items=[
                {
                    # TODO: replace this with the `price` of the product you want to sell
                    'price': '{{PRICE_ID}}',
                    'quantity': 1,
                },
            ],
            payment_method_types=[
              'card',
            ],
            mode='payment',
            success_url=YOUR_DOMAIN + '?success=true',
            cancel_url=YOUR_DOMAIN + '?canceled=true',
        )
    except Exception as e:
        return str(e)

    return redirect(checkout_session.url, code=303)

if __name__ == '__main__':
    app.run(port=4242)

I can't understand where to write this server.py code in my django project. any help will be appreciated. My django project hierarchy