Calling tasks asynchronously in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django Celery task call?

Consider this Django Celery task defined in tasks.py. What will be printed when the task is called asynchronously?

Django

from celery import shared_task

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

result = add.delay(4, 5)
print(result.ready())

A False

B True

C 9

D None

💡 Hint

Think about what delay() returns and when the task finishes.

The delay() method queues the task and returns an AsyncResult immediately. The task is not finished yet, so result.ready() returns False.

❓ state_output

intermediate

What is the value of result.get() after task completion?

Given this Celery task and its asynchronous call, what will result.get() return after the task finishes?

Django

from celery import shared_task

@shared_task
def multiply(x, y):
    return x * y

result = multiply.delay(3, 7)
output = result.get(timeout=10)
print(output)

A 10

B None

C TimeoutError

D 21

💡 Hint

The get() method waits for the task result.

The get() method blocks until the task completes or the timeout expires. Since the task multiplies 3 and 7, the result is 21.

📝 Syntax

advanced

Which option correctly schedules a periodic task in Django Celery?

You want to schedule a task to run every 10 minutes using Django Celery. Which code snippet correctly sets this up in celery.py or tasks.py?

A

from celery.schedules import crontab
app.conf.beat_schedule = {'task-every-10-minutes': {'task': 'myapp.tasks.my_task', 'schedule': crontab(minute='*/10')}}

B app.conf.beat_schedule = {'task-every-10-minutes': {'task': 'myapp.tasks.my_task', 'schedule': 10}}

C

from celery.schedules import schedule
app.conf.beat_schedule = {'task-every-10-minutes': {'task': 'myapp.tasks.my_task', 'schedule': schedule(10)}}

D app.conf.beat_schedule = {'task-every-10-minutes': {'task': 'myapp.tasks.my_task', 'interval': 600}}

💡 Hint

Look for the correct way to specify a periodic schedule using crontab.

Option A uses crontab(minute='*/10') which correctly schedules the task every 10 minutes. Other options either use wrong keys or invalid schedule types.

🔧 Debug

advanced

Why does this asynchronous task call raise an error?

Examine the code below. Why does calling send_email.delay() raise an error?

Django

from celery import shared_task

@shared_task
def send_email(to_address):
    print(f"Sending email to {to_address}")

send_email.delay()

A No error, prints 'Sending email to None'

B SyntaxError due to missing colon in function definition

C TypeError because delay() is called without required argument

D AttributeError because send_email is not a task

💡 Hint

Check the function parameters and how delay() is called.

The send_email task requires one argument to_address. Calling delay() without arguments causes a TypeError.

🧠 Conceptual

expert

Which statement about Django Celery task execution is true?

Select the correct statement about how Django Celery executes asynchronous tasks.

A Tasks run synchronously in the main Django process by default

B Tasks are sent to a message broker and executed by separate worker processes asynchronously

C Calling <code>delay()</code> immediately executes the task in the worker process

D Django automatically retries failed tasks without any configuration

💡 Hint

Think about how Celery separates task execution from the Django app.

Celery sends tasks to a message broker like RabbitMQ or Redis. Worker processes listen to the broker and execute tasks asynchronously, separate from the Django main process.