from telethon import TelegramClient
import sys

api_id = 123456      # From my.telegram.org/apps
api_hash = 'your_api_hash'
phone = '+15555555555'  # Your phone number

async def main():
    message = " ".join(sys.argv[1:]) or "Hello from CLI"
    await client.send_message('me', message)  # Send to yourself or channel username

client = TelegramClient('session_name', api_id, api_hash)
with client:
    client.loop.run_until_complete(main())