Telegram Bot saves the cryptocurrency exchange rate incorrectly. Why is this happening?

Question

Python

I am writing a telegram bot and everything seems to be working for me, but alas, not as it should be. In short, I will say what kind of bot it is. I made a telegram bot that, using a parser, enters the site, reads the bitcoin rate in dollars and sends it to a person after a certain time and compares whether the bitcoin rate has changed. If yes, then it sends a new course value to the person. But I apparently did not correctly save the bitcoin rate so that the bot compares and sends, since it sends alternating values ​​(I attached the screen below).

import telebot
import requests
import time

from bs4 import BeautifulSoup

token = ""
channel_id = ""
bot = telebot.TeleBot(token)

@bot.message_handler(content_types=['text'])
def commands(message):
    #bot.send_message(channel_id, message.text)
    if message.text == "Курс":
        #bot.send_message(channel_id, "Hello")
        back_post_id = None
        while True:
            post_text = parser(back_post_id)
            back_post_id = post_text[1]

            if post_text[0] != None:
                bot.send_message(channel_id, post_text[0])
                time.sleep(1)
    else:
        bot.send_message(message.from_user.id, "Я тебя не понимаю. Напиши Курс")

def parser(back_post_id):
    URL = "https://currency.com/ru/btc-to-usd?utm_course=rbc&utm_campaign=quote"

    page = requests.get(URL)
    soup = BeautifulSoup(page.content, "lxml")

    post = soup.find("b", class_='i-price-buy').text
    post_id = post
    
    if post_id != back_post_id:
        post = soup.find("b", class_='i-price-buy').text
        
        return f"{post}", post_id
    else:
        return None, post_id

bot.polling(none_stop=True, interval=0)

Answer 1

It makes no sense to compare once a second - the market is alive and the exchange rate changes very often, this is not a dollar / euro on cbr.ru.
According to the subject - on the site there is some kind of cached value, which the parser receives. (you can easily check it just by looking at the source https://currency.com/en/btc-to-usd?utm_course=rbc&... )
On the site, the course is updated via a websocket, so it needs to be parsed. We subscribe to the desired cryptocurrency and rejoice

import websocket
import _thread
import json

def on_message(ws, message):
    data = json.loads(json.loads(message)['data'])
    print(data['bid'], data['ask'])

def on_error(ws, error):
    print(error)

def on_close(ws, close_status_code, close_msg):
    print("### closed ###")

def on_open(ws):
    def run(*args):
        ws.send(json.dumps({"event":"pusher:subscribe","data":{"channel":"45076691096786116"}}))
    _thread.start_new_thread(run, ())

if __name__ == "__main__":
    websocket.enableTrace(False)
    ws = websocket.WebSocketApp("wss://prod-pusher.backend-capital.com/app/MvtsstCbm?protocol=7&client=js&version=4.2.2&flash=false",
                              on_open=on_open,
                              on_message=on_message,
                              on_error=on_error,
                              on_close=on_close)

    ws.run_forever()