Sending Telegram messages with Telethon: some entity parameters work, others don't?

Question

I'm using Telethon's send_message function to send messages to various chats.

Sometimes, the destination is another user (just a regular one on one chat), sometimes a group, sometimes a supergroup, and sometimes a channel (of which I'm admin).

If I understand correctly, the syntax is supposed to be:

client.send_message(entity,text)

But I can't figure out what the entity parameter is supposed to be in different cases. What I find especially confusing is specifying an integer id seems to work fine for some groups, but not for others.

For example:

I have a normal 1-to-1 chat with someone who has user_id 11111, and also with another person who has user_id 22222.
Furthermore I'm in two groups (supergroups actually) which have channel_id 33333 and 44444.

I can specify 11111 or 33333 as entity, and the message gets sent correctly (to the first person or the first group respectively). However if I specify 22222 or 44444, I'm getting an error:

Cannot find any entity corresponding to "{}"'.format(string)
ValueError: Cannot find any entity corresponding to "22222"

I am also receiving mesasges from all 4 chats using this same Telethon instance, and that's working all fine.

So my question is: how do I get the correct entity data for send_message()?

Answer 1

I suggest reading this section of the document ([entities][1])

for example, I want to send the message to a user with the username: alix

client = TelegramClient('session_name',
                    api_id,
                    api_hash,
                    )
client.start()
destination_user_username='alix'
entity=client.get_entity(destination_user_username)
client.send_message(entity=entity,message="Hi")

or I want to send the message to a channel with username: test_ali3

client = TelegramClient('session_name',
                    api_id,
                    api_hash
                    )
client.start()

destination_channel_username='test_ali3'
entity=client.get_entity(destination_channel_username)
client.send_message(entity=entity,message="Hi")

or I want to send the message to a group with invite_link: https://t.me/joinchat/Bn4WIhMF1T_ZAF-yM6WbHw

client = TelegramClient('session_name',
                    api_id,
                    api_hash
                    )
client.start()
destination_group_invite_link='https://t.me/joinchat/Bn4WIhMF1T_ZAF-yM6WbHw'
entity=client.get_entity(destination_group_invite_link)
client.send_message(entity=entity,message="Hi")

I hope to be useful to you. [1]: https://docs.telethon.dev/en/stable/concepts/entities.html