Telethon leads to `RuntimeWarning: coroutine 'MessageMethods.send_message' was never awaited`

Question

I'm trying to run this first code snippet provided by the Telethon documentation. But, after multiple problems (here and here), I ended up with this modified version:

import os
import sys
from telethon.sync import TelegramClient, events

# import nest_asyncio
# nest_asyncio.apply()

session_name = "<session_name>"
api_id = <api_id>
api_hash = "<api_hash>"


os.chdir(sys.path[0])

if f"{session_name}.session" in os.listdir():
    os.remove(f"{session_name}.session")

async with TelegramClient(session_name, api_id, api_hash) as client:
   client.send_message('me', 'Hello, myself!')
   print(client.download_profile_photo('me'))

   @client.on(events.NewMessage(pattern='(?i).*Hello'))
   async def handler(event):
      await event.reply('Hey!')

   client.run_until_disconnected()

However now I'm getting these warnings:

usr/local/lib/python3.7/site-packages/ipykernel_launcher.py:23: RuntimeWarning: coroutine 'MessageMethods.send_message' was never awaited
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
/usr/local/lib/python3.7/site-packages/ipykernel_launcher.py:24: RuntimeWarning: coroutine 'DownloadMethods.download_profile_photo' was never awaited
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
/usr/local/lib/python3.7/site-packages/ipykernel_launcher.py:30: RuntimeWarning: coroutine 'UpdateMethods._run_until_disconnected' was never awaited
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

when running the code on Jupyter. Now here are my questions:

• what those warning messages mean and how should I address them?
• what is the expected result of this code if working properly? Should I receive a message in Telegram or something? Because I don't recive any messages other than the signin code.
• What does the @ symbol at the beginning of the @client.on... line mean? what does that line is supposed to do? From this line onwards I do not understand the code. Would appreciate if you could help me understand it.

Answer 1

Just add await the client.send_message('me', 'Hello, myself!') to solve that error and print afterdownload_profile_photo has done its work downloads an image to localhost so that may be why you don't see anything. You should read telethon documentation thoroughly and also how to use photo downloads correctly

All the calls to the client have a delay and should always be awaited so that your code doesn't get blocked. You should read the asyncio tutorial The correct code would be:

async with TelegramClient(session_name, api_id, api_hash) as client:
   await client.send_message('me', 'Hello, myself!')
   print(await client.download_profile_photo('me'))

   @client.on(events.NewMessage(pattern='(?i).*Hello'))
   async def handler(event):
      await event.reply('Hey!')

   #await client.run_until_disconnected()

The @ is a decorator and you should read the PEP related to decorators, but in short words, they execute a function before yours.

In this case @client.on(events.NewMessage means:

When there is a new event that happens to be a message that matches the pattern specified handle it with this function called handler

Answer 2

Jupyter will run the asyncio event loop so that you can use async for / with / await outside of an async def. This conflicts with Telethon's .sync magic which you should try to avoid when using Jupyter, IPython, or similar.

To fix your code:

from telethon import TelegramClient, events
#            ^ note no .sync

session_name = "<session_name>"
api_id = <api_id>
api_hash = "<api_hash>"

async with TelegramClient(session_name, api_id, api_hash) as client:
    await client.send_message('me', 'Hello, myself!')
    # ^ note you need to use `await` in Jupyter
    # we are avoiding the `.sync` magic so it needs to be done by yourself

    print(await client.download_profile_photo('me'))
    #     ^ same here, needs await

    @client.on(events.NewMessage(pattern='(?i).*Hello'))
    async def handler(event):
        await event.reply('Hey!')

    await client.run_until_disconnected()
    # ^ once again needs await

If you want code to run anywhere (Jupyter, Python shell, normal run), just be sure to do everything inside async def:

import asyncio

from telethon import TelegramClient, events

session_name = "<session_name>"
api_id = <api_id>
api_hash = "<api_hash>"

async def main():
    async with TelegramClient(session_name, api_id, api_hash) as client:
       await client.send_message('me', 'Hello, myself!')
       print(await client.download_profile_photo('me'))

       @client.on(events.NewMessage(pattern='(?i).*Hello'))
       async def handler(event):
           await event.reply('Hey!')

       await client.run_until_disconnected()

# Only this line changes, the rest will work anywhere.
# Jupyter
await main()

# Otherwise
asyncio.run(main())