Sending public channel reply Telegram messages with Telethon - telegram

Question

I'm working with Telethon have been able to successfully send messages as well as pull public channel messages sent by other members, but I was wondering if there is a way to reply via sendmessage to an already posted message. The sent reply would be attached to the original posting.
from telethon.sync import TelegramClient
def messages(api_id, api_hash, phone, channel_name, message_content,
destination_channel_id):
client = TelegramClient(phone, api_id, api_hash)
client.connect()
if not client.is_user_authorized():
client.send_code_request(phone)
client.sign_in(phone, input('Enter the code: '))
destination_channel_username = channel_name
entity = client.get_entity(destination_channel_username)
client.send_message(entity, message_content)
client.disconnect()
def channel_chat(api_id, api_hash, phone, chat):
client = TelegramClient(phone, api_id, api_hash)
client.connect()
if not client.is_user_authorized():
client.send_code_request(phone)
client.sign_in(phone, input('Enter the code: '))
for message in client.iter_messages(chat, from_user='me', reverse=True):
return message
quit()
client.disconnect()
if __name__ == "__main__":
api_id = "api_id"
api_hash = "api_hash"
phone = "phone)
chat = "channel_name"
last_message = channel_chat(api_id, api_hash, phone, chat)
if last_message:
print("ID{} - {}".format(last_message.id, last_message.message))
messages(api_id, api_hash, phone, chat, 'Thank you', last_message.id)

Answer 1

You can use the reply_to parameter of send_message to reply to a specific message:
client.send_message(entity, message_content, reply_to=msg_id_of_destination_channel)
This will work as long as the message you're trying to reply to exists in the chat where your new message is being sent. You may need to define a dict which maps the identifiers of all messages between the two channels if all you have is the message ID of the source channel.
As a side note, this is a very expensive operation:
entity = client.get_entity(destination_channel_username)
You should consider using get_input_entity, and cache the result.