How can I send a message to someone with my telegram bot using their Username

Question

I am using the telepot python library, I know that you can send a message when you have someone's UserID(Which is a number). I wanna know if it is possible to send a message to someone without having their UserID but only with their username(The one which starts with '@'), Also if there is a way to convert a username to a UserID.

Answer 1

1. Post one message from User to the Bot.
2. Open https://api.telegram.org/bot<Bot_token>/getUpdates page.
3. Find this message and navigate to the result->message->chat->id key.
4. Use this ID as the [chat_id] parameter to send personal messages to the User.

Answer 2

It is only possible to send messages to users whom have already used /start on your bot. When they start your bot, you can find update.message.from.user_id straight from the message they sent /start with, and you can find update.message.from.username using the same method. In order to send a message to "@Username", you will need them to start your bot, and then store the username with the user_id. Then, you can input the username to find the correct user_id each time you want to send them a message.