Task results and status in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django view when a task is completed?

Consider a Django view that checks a task's status and returns a message accordingly.

from django.http import JsonResponse
from django.views import View

class TaskStatusView(View):
    def get(self, request, task_id):
        task = get_task_by_id(task_id)  # Returns a dict with 'status'
        if task['status'] == 'completed':
            return JsonResponse({'result': 'Task finished successfully'})
        else:
            return JsonResponse({'result': 'Task still running'})

What will be the JSON response if task['status'] is 'completed'?

Django

from django.http import JsonResponse
from django.views import View

class TaskStatusView(View):
    def get(self, request, task_id):
        task = {'status': 'completed'}
        if task['status'] == 'completed':
            return JsonResponse({'result': 'Task finished successfully'})
        else:
            return JsonResponse({'result': 'Task still running'})

A {"status": "completed"}

B {"result": "Task still running"}

C {"error": "Task not found"}

D {"result": "Task finished successfully"}

💡 Hint

Check the condition that matches the task status.

The view returns a JSON response with {'result': 'Task finished successfully'} when the task status is 'completed'.

❓ state_output

intermediate

What is the value of task_status after running this Django signal handler?

Given this Django signal handler that updates a task's status after completion:

from django.dispatch import receiver
from django.db.models.signals import post_save

@receiver(post_save, sender=Task)
def update_task_status(sender, instance, **kwargs):
    if instance.is_finished:
        instance.status = 'completed'
        instance.save()

# Assume a Task instance with is_finished=True and initial status='pending'

What will be the status of the task after the signal runs?

Django

class Task:
    def __init__(self, is_finished, status):
        self.is_finished = is_finished
        self.status = status
    def save(self):
        pass

task = Task(is_finished=True, status='pending')
if task.is_finished:
    task.status = 'completed'
    task.save()
task_status = task.status

A failed

B pending

C completed

D None

💡 Hint

Check what happens when is_finished is True.

The signal sets the status to 'completed' if is_finished is True, so the final status is 'completed'.

📝 Syntax

advanced

Which option correctly defines a Django model field to track task status with choices?

You want to define a Django model field status that only allows 'pending', 'running', or 'completed'. Which code snippet is correct?

A status = models.CharField(max_length=10, choices=('pending', 'running', 'completed'))

B status = models.CharField(max_length=10, choices=[('pending', 'Pending'), ('running', 'Running'), ('completed', 'Completed')])

C status = models.CharField(max_length=10, choices={'pending': 'Pending', 'running': 'Running', 'completed': 'Completed'})

D status = models.CharField(max_length=10, choices=[('pending'), ('running'), ('completed')])

💡 Hint

Choices must be a list of tuples pairing database value and human-readable name.

Option B correctly uses a list of tuples for choices. Option B uses a dict which is invalid. Option B uses a tuple of strings without pairs. Option B uses a list of strings without tuples.

🔧 Debug

advanced

Why does this Django async task status check raise an error?

Given this async function to check a task status:

async def check_task_status(task_id):
    task = Task.objects.get(id=task_id)
    if task.status == 'completed':
        return 'Done'
    else:
        return 'In progress'

When called in an async context, it raises an error. Why?

A Django ORM methods like get() are synchronous and cannot be awaited in async functions

B The function is missing an await keyword before Task.objects.get()

C The task.status field is not accessible in async functions

D Async functions cannot return strings in Django

💡 Hint

Consider how Django ORM works with async code.

Django ORM methods like get() are synchronous and block the event loop if called in async functions without special async ORM support.

🧠 Conceptual

expert

Which Django feature best tracks task results and status asynchronously?

You want to run long tasks in the background and check their status and results later in Django. Which feature is best suited for this?

A Using Celery with Django to run tasks asynchronously and store results

B Using Django middleware to intercept and track task status

C Using Django Channels to handle WebSocket connections for task updates

D Using Django's built-in management commands to run tasks synchronously

💡 Hint

Think about background task queues and result storage.

Celery integrates with Django to run tasks asynchronously and track their status and results efficiently.