Extensions – Your first Bot

Abhai Kollara Dilip edited this page Sep 10, 2018 · 24 revisions

Introduction

The telegram.ext submodule is built on top of the pure API implementation. It provides an easy-to-use interface and takes some work off the programmer, so you don't have to repeat yourself.

It consists of several classes, but the two most important ones are telegram.ext.Updater and telegram.ext.Dispatcher.

The Updater class continuously fetches new updates from telegram and passes them on to the Dispatcher class. If you create an Updater object, it will create a Dispatcher for you and link them together with a Queue. You can then register handlers of different types in the Dispatcher, which will sort the updates fetched by the Updater according to the handlers you registered, and deliver them to a callback function that you defined.

Every handler is an instance of any subclass of the telegram.ext.Handler class. The library provides handler classes for almost all use cases, but if you need something very specific, you can also subclass Handler yourself.

To begin, you'll need an Access Token. If you already read and followed Introduction to the API, you can use the one you generated then. If not: To generate an Access Token, you have to talk to @BotFather and follow a few simple steps (described here). You should really read the introduction first, though.

Your first Bot, step-by-step

So, let's get started! Again, please fire up a Python command line if you want to follow this tutorial.

First, you have to create an Updater object. Replace 'TOKEN' with your Bot's API token.

from telegram.ext import Updater
updater = Updater(token='TOKEN')

Related docs: telegram.ext.Updater

For quicker access to the Dispatcher used by your Updater, you can introduce it locally:

dispatcher = updater.dispatcher

This is a good time to set up the logging module, so you will know when (and why) things don't work as expected:

import logging
logging.basicConfig(format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
                     level=logging.INFO)

Note: Read the article on Exception Handling if you want to learn more.

Now, you can define a function that should process a specific type of update:

def start(bot, update):
    bot.send_message(chat_id=update.message.chat_id, text="I'm a bot, please talk to me!")

Related docs: sendMessage

The goal is to have this function called every time the Bot receives a Telegram message that contains the /start command. To accomplish that, you can use a CommandHandler (one of the provided Handler subclasses) and register it in the dispatcher:

from telegram.ext import CommandHandler
start_handler = CommandHandler('start', start)
dispatcher.add_handler(start_handler)

Related docs: telegram.ext.CommandHandler, telegram.ext.Dispatcher.add_handler

And that's all you need. To start the bot, run:

updater.start_polling()

Related docs: telegram.ext.Updater.start_polling

Give it a try! Start a chat with your bot and issue the /start command - if all went right, it will reply.

But our Bot can now only answer to the /start command. Let's add another handler that listens for regular messages. Use the MessageHandler, another Handler subclass, to echo to all text messages:

def echo(bot, update):
    bot.send_message(chat_id=update.message.chat_id, text=update.message.text)

from telegram.ext import MessageHandler, Filters
echo_handler = MessageHandler(Filters.text, echo)
dispatcher.add_handler(echo_handler)

Related docs: telegram.ext.MessageHandler

From now on, your bot should echo all non-command messages it receives.

Note: As soon as you add new handlers to dispatcher, they are in effect.

Note: The Filters class contains a number of functions that filter incoming messages for text, images, status updates and more. Any message that returns True for at least one of the filters passed to MessageHandler will be accepted. You can also write your own filters if you want. See more in Advanced Filters.

Let's add some actual functionality to your bot. We want to implement a /caps command that will take some text as an argument and reply to it in CAPS. To make things easy, you can receive the arguments (as a list, split on spaces) that were passed to a command in the callback function:

def caps(bot, update, args):
    text_caps = ' '.join(args).upper()
    bot.send_message(chat_id=update.message.chat_id, text=text_caps)

caps_handler = CommandHandler('caps', caps, pass_args=True)
dispatcher.add_handler(caps_handler)

Note: Take a look at the pass_args=True in the CommandHandler initiation. This is required to let the handler know that you want it to pass the list of command arguments to the callback. All handler classes have keyword arguments like this. Some are the same among all handlers, some are specific to the handler class. If you use a new type of handler for the first time, look it up in the docs and see if one of them is useful to you.

Another cool feature of the Telegram Bot API is the inline mode. If you want to implement inline functionality for your bot, please first talk to @BotFather and enable inline mode using /setinline. It sometimes takes a while until your Bot registers as an inline bot on your client. You might be able to speed up the process by restarting your Telegram App (or sometimes, you just have to wait for a while).

As your bot is obviously a very loud one, let's continue with this theme for inline. You probably know the process by now, but there are a number of new types used here, so pay some attention:

from telegram import InlineQueryResultArticle, InputTextMessageContent
def inline_caps(bot, update):
    query = update.inline_query.query
    if not query:
        return
    results = list()
    results.append(
        InlineQueryResultArticle(
            id=query.upper(),
            title='Caps',
            input_message_content=InputTextMessageContent(query.upper())
        )
    )
    bot.answer_inline_query(update.inline_query.id, results)

from telegram.ext import InlineQueryHandler
inline_caps_handler = InlineQueryHandler(inline_caps)
dispatcher.add_handler(inline_caps_handler)

Related docs: telegram.ext.InlineQueryHandler, answerInlineQuery

Not bad! Your Bot can now yell on command (ha!) and via inline mode.

Some confused users might try to send commands to the bot that it doesn't understand, so you can use a MessageHandler with a command filter to reply to all commands that were not recognized by the previous handlers.

def unknown(bot, update):
    bot.send_message(chat_id=update.message.chat_id, text="Sorry, I didn't understand that command.")

unknown_handler = MessageHandler(Filters.command, unknown)
dispatcher.add_handler(unknown_handler)

Note: This handler must be added last. If you added it sooner, it would be triggered before the CommandHandlers had a chance to look at the update. Once an update is handled, all further handlers are ignored. To circumvent this, you can pass the keyword argument group (int) to add_handler with a value other than 0.

If you're done playing around, stop the bot with:

updater.stop()

Note: As you have read earlier, the Updater runs in a separate thread. That is very nice for this tutorial, but if you are writing a script, you probably want to stop the Bot by pressing Ctrl+C or sending a signal to the Bot process. To do that, use updater.idle(). It blocks execution until one of those two things occur, then calls updater.stop() and then continues execution of the script.

What to read next?

Learn about the library exceptions and best practices in Exception Handling.

You want more features? Check out Extensions – JobQueue!

Or: Get inspired by our example Bots in the examples folder.

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