TelegramBot.py:

from time import sleep
import sys
import telegram
from telegram.ext import Updater, CommandHandler, MessageHandler, Filters


tokenString = ''

class TelegramBot(object):
    def __init__(self):
        self.s = Updater(token=tokenString)

    def start(update, context):
        update.message.reply_text('Hi!')


main file:

import TelegramBot

bot = TelegramBot()
dp = bot.dispatcher
dp.add_handler(CommandHandler("start", bot.start))