Celery installation and setup in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import Celery in your Django project.

Django

from celery import [1]

Drag options to blanks, or click blank then click option'

Aapp

BCelery

Ctask

Dworker

Attempts:

3 left

💡 Hint

Common Mistakes

Importing 'app' or 'task' instead of 'Celery'.

Using lowercase 'celery'.

You import Celery class from the celery package to create a Celery app instance.

2fill in blank

medium

Complete the code to create a Celery app instance named 'app'.

Django

app = Celery('[1]')

Drag options to blanks, or click blank then click option'

Amyproject

Bcelery_app

Cdjango_project

Dtasks

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'celery_app' or 'tasks' which are not project names.

Using 'django_project' as a generic name.

The argument is usually your Django project name, here 'myproject'.

3fill in blank

hard

Fix the error in the code to load Django settings into Celery.

Django

app.config_from_object('[1]')

Drag options to blanks, or click blank then click option'

Adjango.settings

Bsettings

Cdjango.conf.settings

Ddjango.conf:settings

Attempts:

3 left

💡 Hint

Common Mistakes

Using dot notation instead of colon.

Using just 'settings' without module.

The correct string to load Django settings is 'django.conf:settings'.

4fill in blank

hard

Fill both blanks to auto-discover tasks in Django apps.

Django

app.[1]_tasks()  # Auto-discover tasks in installed apps

app.conf.broker_url = '[2]'

Drag options to blanks, or click blank then click option'

Aautodiscover

Bredis://localhost:6379/0

Cdiscover

Damqp://guest@localhost//

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'discover_tasks' instead of 'autodiscover_tasks'.

Using AMQP URL when Redis is expected.

autodiscover_tasks() finds tasks.py files in apps.
The broker URL here uses Redis on localhost.

5fill in blank

hard

Fill all three blanks to define a simple Celery task function.

Django

from celery import shared_task

@shared_task
def [1](x, y):
    return x [2] y  # Returns sum

result = [3](4, 5).delay()

Drag options to blanks, or click blank then click option'

Aadd

B+

Dsum

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sum' as function name which is a built-in function.

Using '-' or '*' instead of '+'.

The task function is named 'add'. It returns the sum using '+'.
The task is called by its name 'add' with .delay() to run asynchronously.

Practice

1. What is the main purpose of using Celery in a Django project?

easy

A. To replace Django's built-in ORM

B. To create database models automatically

C. To style the frontend of the Django app

D. To run time-consuming tasks in the background without blocking the main app

Solution

1. Step 1: Understand Celery's role

   Celery is a tool for running tasks asynchronously, meaning it handles tasks in the background.

2. Step 2: Compare options

   Creating database models automatically, styling the frontend of the Django app, and replacing Django's built-in ORM are unrelated to Celery; only running time-consuming tasks in the background without blocking the main app correctly describes its purpose.

3. Final Answer:

   To run time-consuming tasks in the background without blocking the main app -> Option D

4. Quick Check:

   Celery = background task runner [OK]

Hint: Celery runs slow tasks behind scenes to keep app fast [OK]

Common Mistakes:

• Thinking Celery manages database models
• Confusing Celery with frontend styling tools
• Assuming Celery replaces Django ORM

2. Which command correctly installs Celery and Redis as the message broker for a Django project?

easy

A. pip install celery redis

B. pip install django-celery

C. pip install celery-django redis-server

D. pip install celery-redis

Solution

1. Step 1: Identify the correct packages

   Celery requires the 'celery' package and a broker like Redis, installed via 'redis' package.

2. Step 2: Evaluate commands

   Only 'pip install celery redis' installs both needed packages correctly; others are incorrect or non-existent.

3. Final Answer:

   pip install celery redis -> Option A

4. Quick Check:

   Install celery and redis packages = pip install celery redis [OK]

Hint: Use pip install celery redis to get both packages [OK]

Common Mistakes:

• Installing 'django-celery' which is outdated
• Using non-existent package names
• Forgetting to install Redis client

3. Given this Celery task in Django:

@shared_task
def add(x, y):
    return x + y

result = add.delay(4, 5)
print(result.get(timeout=10))

What will be printed when this code runs correctly?

medium

A. 9

B. delay object

C. None

D. Error: get() not found

Solution

1. Step 1: Understand task execution

   The task 'add' runs asynchronously; calling 'delay(4, 5)' queues the task to add 4 and 5.

2. Step 2: Retrieve result with get()

   'result.get(timeout=10)' waits for the task to finish and returns the sum 9.

3. Final Answer:

   9 -> Option A

4. Quick Check:

   add(4,5) = 9 [OK]

Hint: delay queues task; get() fetches result [OK]

Common Mistakes:

• Expecting delay() to return result immediately
• Confusing task object with result value
• Not using get() to wait for task completion

4. You wrote this Celery setup in your Django project:

from celery import Celery
app = Celery('proj')
app.config_from_object('django.conf:settings', namespace='CELERY')
app.autodiscover_tasks()

But your tasks are not running. What is the most likely mistake?

medium

A. Using wrong Celery import statement

B. Not running a message broker like Redis or RabbitMQ

C. Missing @shared_task decorator on tasks

D. Not calling app.start() in settings.py

Solution

1. Step 1: Check broker setup

   Celery needs a running message broker (Redis or RabbitMQ) to send and receive tasks.

2. Step 2: Analyze other options

   Imports and decorators are correct; app.start() is not required in settings.py; missing broker is common cause.

3. Final Answer:

   Not running a message broker like Redis or RabbitMQ -> Option B

4. Quick Check:

   Broker must run for tasks to work [OK]

Hint: Always start Redis or RabbitMQ before Celery workers [OK]

Common Mistakes:

• Forgetting to start Redis or RabbitMQ server
• Assuming Celery works without a broker
• Misplacing @shared_task decorator

5. You want to configure Celery in your Django project to use Redis as the broker and ensure tasks are auto-discovered. Which of the following is the correct minimal setup in your celery.py file?

hard

A. from celery import Celery
app = Celery('proj')
app.config_from_object('settings')
app.autodiscover_tasks()

B. from celery import Celery
app = Celery('proj')
app.config_from_object('django.conf:settings', namespace='CELERY')
app.autodiscover_tasks()

C. from celery import Celery
app = Celery('proj', broker='redis://localhost:6379/0')
app.autodiscover_tasks()

D. from celery import Celery
app = Celery('proj')
app.broker_url = 'redis://localhost:6379/0'
app.autodiscover_tasks()

Solution

1. Step 1: Set broker URL directly in Celery instance

   from celery import Celery app = Celery('proj', broker='redis://localhost:6379/0') app.autodiscover_tasks() correctly passes Redis broker URL when creating Celery app, which is a minimal working setup.

2. Step 2: Evaluate other options

   The first uses an invalid path to settings ('settings' instead of 'django.conf:settings'); the second requires defining CELERY_BROKER_URL in Django settings.py first; the third is correct syntax-wise but setting broker_url attribute after creation is less minimal than passing in constructor.

3. Final Answer:

   from celery import Celery app = Celery('proj', broker='redis://localhost:6379/0') app.autodiscover_tasks() -> Option C

4. Quick Check:

   Broker URL in constructor = from celery import Celery app = Celery('proj', broker='redis://localhost:6379/0') app.autodiscover_tasks() [OK]

Hint: Pass broker URL directly to Celery constructor for quick setup [OK]

Common Mistakes:

• Setting broker_url attribute instead of passing in constructor
• Misconfiguring config_from_object with wrong settings path
• Omitting broker URL causing connection failure