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Extensions – JobQueue

shelban edited this page Mar 10, 2021 · 30 revisions

Introduction

The extension class telegram.ext.JobQueue allows you to perform tasks with a delay or even periodically, at a set interval. Among many other things, you can use it to send regular updates to your subscribers.

When working with JobQueue, please keep in mind:

  • PTBs JobQueue provides an easy to use and ready to use way of scheduling tasks in a way that ties in with the PTB architecture
  • Managing scheduling logic is not the main intend of PTB and hence as of v13 a third party library is used
  • If you need highly customized scheduling thingies, you can use advanced features of the third party library
  • We can't guarantee that the backend will stay the same forever. For example, if the third party library is discontinued, we will have to look for alternatives.

Example

In addition to the tutorial below there is also the timerbot.py example at the examples directory.

Usage

The JobQueue class is tightly integrated with other telegram.ext classes. Similar to Updater and Dispatcher, it runs asynchronously in a separate thread.

To use the JobQueue, you don't have to do much. When you instantiate the Updater, it will create a JobQueue for you:

from telegram.ext import Updater

u = Updater('TOKEN', use_context=True)
j = u.job_queue

This job queue is also linked to the dispatcher, which is discussed later in this article. Just know that unless you have a good reason to do so, you should not instantiate JobQueue yourself.

Tasks in the job queue are encapsulated by the Job class. It takes a callback function as a parameter, which will be executed when the time comes. This callback function always takes one parameter: context, a telegram.ext.CallbackContext. Like in the case of handler callbacks used by the Dispatcher, through this object you can access context.bot, the Updater's telegram.Bot instance; and for this particular case you can also access context.job, which is the Job instance of the task that triggered the callback (more on that later).

You can use the following methods to create jobs with different frequency and time: job_queue.run_once, job_queue.run_repeating, job_queue.run_daily and job_queue.run_monthly. (As before, you do not usually need to instantiate the Job class directly.)

Tutorial

Add your first job to the queue by defining a callback function and adding it to the job queue. For this tutorial, you can replace '@examplechannel' with a channel where your bot is an admin, or by your user id (use @userinfobot to find out your user id):

def callback_minute(context: telegram.ext.CallbackContext):
    context.bot.send_message(chat_id='@examplechannel', 
                             text='One message every minute')

job_minute = j.run_repeating(callback_minute, interval=60, first=10)

The callback_minute function will be executed every 60.0 seconds, the first time being after 10 seconds (because of first=10). The interval and first parameters are in seconds if they are int or float. They can also be datetime objects. See the docs for detailed explanation. The return value of these functions are the Job objects being created. You don't need to store the result of run_repeating (which is the newly instantiated Job) if you don't need it; we will make use of it later in this tutorial.

You can also add a job that will be executed only once, with a delay:

def callback_30(context: telegram.ext.CallbackContext):
    context.bot.send_message(chat_id='@examplechannel', 
                             text='A single message with 30s delay')

j.run_once(callback_30, 30)

In thirty seconds you should receive the message from callback_30.

If you are tired of receiving a message every minute, you can temporarily disable a job or even completely remove it from the queue:

job_minute.enabled = False  # Temporarily disable this job
job_minute.schedule_removal()  # Remove this job completely

Note: schedule_removal does not immediately remove the job from the queue. Instead, it is marked for removal and will be removed as soon as its current interval is over (it will not run again after being marked for removal).

You might want to add jobs in response to certain user input, and there is a convenient way to do that. The context argument of your Handler callbacks has the JobQueue attached as context.job_queue ready to be used. Another feature you can use here is the context keyword argument of Job. You can pass any object as a context parameter when you launch a Job and retrieve it at a later stage as long as the Job exists. Let's see how it looks in code:

from telegram.ext import CommandHandler
def callback_alarm(context: telegram.ext.CallbackContext):
    context.bot.send_message(chat_id=context.job.context, text='BEEP')

def callback_timer(update: telegram.Update, context: telegram.ext.CallbackContext):
    context.bot.send_message(chat_id=update.message.chat_id,
                             text='Setting a timer for 1 minute!')

    context.job_queue.run_once(callback_alarm, 60, context=update.message.chat_id)

timer_handler = CommandHandler('timer', callback_timer)
u.dispatcher.add_handler(timer_handler)

By placing the chat_id in the Job object, the callback function knows where it should send the message.

All good things must come to an end, so when you stop the Updater, the related job queue will be stopped as well:

u.stop()

Of course, you can instead also stop the job queue by itself:

j.stop()
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