How to create periodic tasks with Celery 4 and Celery 5

Let's analyze the usage of periodic tasks as a useful example. Our task is to get information about a free ebook from Packt Publishing (it could be any other site). We'd like to have an email every day at 7.00 AM with the title of this book.

Let's look at how to do it with Celery (both 4 and 5 versions) and Django. In both cases 'sd' is the name of my Django's project. I've separated my settings into a few parts and 'settings.production' part is information that I've got a 'production.py' file in the 'settings' directory.

For Celery 4:

    in the directory of the Django's project, we should create a standard celery.py file:

import os
from celery import Celery

os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'settings.production')

app = Celery('sd')
app.config_from_object('django.conf:settings', namespace='CELERY')
app.autodiscover_tasks()

    in the '__init__.py' of the project we should add this one line:

__all__ = ['celery_app']

    inside one of the applications we should create 'tasks.py' file:

import requests

from bs4 import BeautifulSoup

from django.core.mail import EmailMessage
from celery.schedules import crontab
from celery.task import periodic_task


@periodic_task(run_every=(crontab(minute=0, hour=7)),
               name='task_send_email_about_ebook',
               ignore_result=True
               )
def task_send_email_about_ebook():
    page = requests.get('https://www.packtpub.com/free-learning')
    soup = BeautifulSoup(page.content, 'html.parser')
    book_title = soup.find('h3', attrs={'class': 'product-info__title'}).text.split('-', 1)[1].strip()
    subject = "Your free e-book from PacktPub is available!"
    message = f"Your new e-book is '{book_title}'. \n"
    message += f"Book is available at <a href='https://www.packtpub.com/packt/offers/free-learning'>Free Learning</a>."
    email = EmailMessage(subject,
                         message,
                         'from@domaine.com',
                         ['to@somedomain.com'])
    email.send(fail_silently=False)

For Celery 5:

    in the directory of the Django's project, we should create a standard 'celery.py' file:

import os
from celery import Celery

# set the default Django settings module for the 'celery' program.
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'settings.production')

app = Celery('sd')

app.config_from_object('django.conf:settings', namespace='CELERY')
app.autodiscover_tasks()

    in the '__init__.py' of the project we should add this one line:

from .celery import app as celery_app

    inside one of the applications we should create 'tasks.py' file:

import requests

from bs4 import BeautifulSoup
from celery.schedules import crontab
from django.core.mail import EmailMessage

from sd.celery import app


@app.task
def task_send_email_about_ebook():
    page = requests.get('https://www.packtpub.com/free-learning')
    soup = BeautifulSoup(page.content, 'html.parser')
    book_title = soup.find('h3', attrs={'class': 'product-info__title'}).text.split('-', 1)[1].strip()
    subject = "Your free e-book from PacktPub is available!"
    message = f"Your new e-book is '{book_title}'. \n"
    message += f"Book is available at <a href='https://www.packtpub.com/packt/offers/free-learning'>Free Learning</a>."
    email = EmailMessage(subject,
                         message,
                         'from@domaine.com',
                         ['to@somedomain.com'])
    email.send(fail_silently=False)


app.conf.beat_schedule = {
    "task_send_email_about_ebook": {
        "task": "frontend.tasks.task_send_email_about_ebook",
        "schedule": crontab(hour=7, minute=0)
        }
    }

The difference between the two versions of Celery in defining periodic tasks is not so spectacular, but it is worth knowing it.