Read public channel texts using Telegram API

Question

I would like to create a small script that will fetch Telegram texts from a public channel (I am not the channel's admin).

I've found another question asked here: Read the messages of the public channels from Telegram
I've tried using Telethon as said in the answer, but it didn't work:

from telethon.tl.functions.contacts import ResolveUsernameRequest
import telethon

client = telethon.TelegramClient("session.txt", api_id=XYZ, api_hash='XYZ')
client.connect()
response = client.invoke(ResolveUsernameRequest("test"))
print(response.channel_id)
print(response.access_hash)

Throwing this error:

C:/Users/mypc/PycharmProjects/untitled/aa.py:5: RuntimeWarning: coroutine 'TelegramBaseClient.connect' was never awaited
  client.connect()
RuntimeWarning: Enable tracemalloc to get the object allocation traceback
Traceback (most recent call last):
  File "C:/Users/mypc/PycharmProjects/untitled/aa.py", line 6, in <module>
    response = client.invoke(ResolveUsernameRequest("test"))
AttributeError: 'TelegramClient' object has no attribute 'invoke'

I've tried reading the API documentation, but I didn't fully understand how those calls work:

https://core.telegram.org/method/channels.exportMessageLink

https://core.telegram.org/method/channels.joinChannel

https://core.telegram.org/method/channels.getMessages

I'd be grateful if someone could explain to me how those work.

Callihan

client.invoke(request) is the old way to do it. You need to use client(request). – Gary

See this answer for how to read channel past messages using a user account. – Platte

Answer 1

That answer is very old. If we check Telethon's Quick-Start we have enough code to do what you need:

from telethon import TelegramClient

# Remember to use your own values from my.telegram.org!
api_id = 12345
api_hash = '0123456789abcdef0123456789abcdef'
client = TelegramClient('anon', api_id, api_hash)

async def main():
    # You can print the message history of any chat:
    async for message in client.iter_messages('USERNAME OF THE CHANNEL'):
        print(message.sender.username, message.text)

with client:
    client.loop.run_until_complete(main())

Lapsus

But, how do you connect your bot to listen public channel messages? Your code does not answer the question. – Raffle

The code answers the question fine ("fetch text from a public channel"). Actively listen for incoming messages is a different question. – Lapsus

Answer 2

Well like it says, TelegramClient has no invoke method. Have you tried client(ResolveUsernameRequest("test"))?

Actionable

It would be more helpful to note that invoke was the old way of doing it, and refer to the page that explains how full API is done. In addition, there's a friendly method which is a far better alternative. – Lapsus

Fair. I didn't know it was the old way of doing it, seeing as I'm still fairly new to Telethon – Actionable