Async views basics in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this async Django view?

Consider this async Django view. What will the client receive as a response body?

Django

from django.http import JsonResponse
import asyncio

async def my_view(request):
    await asyncio.sleep(0.1)
    return JsonResponse({'message': 'Hello async'})

A TypeError: object JsonResponse can't be awaited

B {"message": "Hello async"}

C HttpResponse with empty body

D RuntimeError: This event loop is already running

💡 Hint

Async views can use await inside and return normal HttpResponse or JsonResponse objects.

Async views in Django can use await for async operations like asyncio.sleep. Returning JsonResponse sends JSON data as HTTP response body.

📝 Syntax

intermediate

Which option correctly defines an async Django view?

Select the option that correctly defines an async Django view function.

A def view(request): await HttpResponse('Hi')

B def async view(request): return HttpResponse('Hi')

C async def view(request): return HttpResponse('Hi')

D async def view(request): await HttpResponse('Hi')

💡 Hint

Async views must be defined with async def and can return HttpResponse directly.

Option C correctly uses async def and returns HttpResponse. Option C has invalid syntax. Option C tries to await a non-awaitable. Option C uses await outside async function.

🔧 Debug

advanced

What error occurs when awaiting a synchronous Django ORM call in async view?

Given this async view snippet, what error will it raise? async def view(request): user = await User.objects.get(id=1) return HttpResponse(user.username)

A TypeError: 'User' object is not awaitable

B RuntimeError: Cannot run sync code in async context

C OperationalError: database connection lost

D No error, returns username

💡 Hint

Django ORM calls are synchronous and cannot be awaited directly.

Django ORM methods like get() are synchronous and return model instances, which are not awaitable. Awaiting them causes TypeError.

❓ state_output

advanced

What is the order of printed output in this async Django view?

Analyze the following async view and determine the order of printed lines in the server console.

Django

import asyncio
from django.http import HttpResponse

async def view(request):
    print('Start')
    await asyncio.sleep(0.05)
    print('Middle')
    await asyncio.sleep(0.05)
    print('End')
    return HttpResponse('Done')

A Start, Middle, End

B Start, End, Middle

C End, Middle, Start

D Middle, Start, End

💡 Hint

Await pauses execution until the awaited task completes.

The prints happen sequentially with awaits in between, so output order is Start, Middle, End.

🧠 Conceptual

expert

Which statement about Django async views is TRUE?

Select the true statement about async views in Django.

A Async views can directly call synchronous ORM methods without issues.

B Async views must always return JsonResponse objects.

C Async views run in a separate thread by default.

D Async views allow awaiting asynchronous code but must avoid blocking sync calls.

💡 Hint

Think about how async views handle async and sync code.

Async views can await async code but synchronous blocking calls like ORM must be handled carefully (e.g., using sync_to_async). They do not run in separate threads by default and can return any HttpResponse subclass.

Practice

1. What is the main benefit of using async views in Django?

easy

A. They allow Django to handle many requests without waiting for slow tasks.

B. They automatically speed up CPU-heavy calculations.

C. They replace the need for a database in your app.

D. They make your app use less memory by default.

Solution

1. Step 1: Understand what async views do

   Async views let Django pause a request while waiting for slow tasks like network calls, so it can handle other requests meanwhile.

2. Step 2: Compare options to this behavior

   Only They allow Django to handle many requests without waiting for slow tasks. correctly describes this benefit. Options B, C, and D are incorrect because async views do not speed up CPU tasks, replace databases, or reduce memory automatically.

3. Final Answer:

   They allow Django to handle many requests without waiting for slow tasks. -> Option A

4. Quick Check:

   Async views improve concurrency = A [OK]

Hint: Async views help handle many requests without blocking [OK]

Common Mistakes:

• Thinking async speeds up CPU-heavy tasks
• Believing async removes the need for a database
• Assuming async reduces memory usage automatically

2. Which of the following is the correct way to define an async view in Django?

easy

A. def my_view(request): return HttpResponse('Hello')

B. async def my_view(request): return HttpResponse('Hello')

C. async def my_view(request): await HttpResponse('Hello')

D. def async my_view(request): return HttpResponse('Hello')

Solution

1. Step 1: Recall async view syntax

   Async views must be defined with async def and can return a response directly.

2. Step 2: Check each option

   async def my_view(request): return HttpResponse('Hello') correctly uses async def and returns a response. def my_view(request): return HttpResponse('Hello') is a normal sync view. async def my_view(request): await HttpResponse('Hello') wrongly uses await on a response object, which is not awaitable. def async my_view(request): return HttpResponse('Hello') has invalid syntax.

3. Final Answer:

   async def my_view(request): return HttpResponse('Hello') -> Option B

4. Quick Check:

   Async view syntax = async def [OK]

Hint: Async views start with 'async def' keyword [OK]

Common Mistakes:

• Using 'def' instead of 'async def'
• Awaiting non-awaitable objects like HttpResponse
• Incorrect function declaration syntax

3. What will the following async view return when called?

from django.http import HttpResponse
import asyncio

async def my_view(request):
    await asyncio.sleep(1)
    return HttpResponse('Done')

medium

A. Returns 'Done' after 1 second delay

B. Returns immediately with 'Done'

C. Raises a SyntaxError

D. Returns None

Solution

1. Step 1: Analyze the async view code

   The view awaits asyncio.sleep(1), which pauses for 1 second asynchronously before continuing.

2. Step 2: Determine the response behavior

   After the 1 second pause, it returns an HttpResponse with 'Done'. So the client receives 'Done' after 1 second.

3. Final Answer:

   Returns 'Done' after 1 second delay -> Option A

4. Quick Check:

   Await asyncio.sleep delays response = B [OK]

Hint: Await pauses async view before returning response [OK]

Common Mistakes:

• Thinking the response is immediate despite await
• Confusing syntax errors with valid async/await usage
• Assuming None is returned without explicit return

4. Identify the error in this async view code:

async def my_view(request):
    response = HttpResponse('Hello')
    await response
    return response

medium

A. HttpResponse must be awaited to send the response.

B. Missing 'async' keyword before function definition.

C. The function should return a string, not HttpResponse.

D. HttpResponse object is not awaitable, so 'await response' causes an error.

Solution

1. Step 1: Check usage of await

   The code tries to 'await response' where response is an HttpResponse object, which is not awaitable.

2. Step 2: Understand correct async view behavior

   HttpResponse objects are returned directly without awaiting. Awaiting a non-awaitable causes a runtime error.

3. Final Answer:

   HttpResponse object is not awaitable, so 'await response' causes an error. -> Option D

4. Quick Check:

   Only await awaitable objects = C [OK]

Hint: Only await async functions or awaitables, not HttpResponse [OK]

Common Mistakes:

• Awaiting HttpResponse objects
• Forgetting async keyword on function
• Returning wrong types from views

5. You want to fetch data from an external API inside a Django async view. Which approach correctly uses async/await to avoid blocking the server?

import httpx

async def fetch_data():
    async with httpx.AsyncClient() as client:
        response = await client.get('https://api.example.com/data')
        return response.json()

async def my_view(request):
    data = fetch_data()
    return JsonResponse(data)

hard

A. Replace async def with def in fetch_data to fix it.

B. Call fetch_data() without await; it runs synchronously.

C. Await fetch_data() inside my_view to get the data asynchronously.

D. Use requests.get() instead of httpx.AsyncClient for async calls.

Solution

1. Step 1: Identify async call usage

   fetch_data is an async function returning a coroutine. To get its result, you must await it inside an async view.

2. Step 2: Check the given my_view code

   my_view calls fetch_data() without await, so data is a coroutine, not the actual data. This will cause errors or wrong behavior.

3. Step 3: Correct usage

   Use data = await fetch_data() inside my_view to get the awaited result asynchronously.

4. Final Answer:

   Await fetch_data() inside my_view to get the data asynchronously. -> Option C

5. Quick Check:

   Await async functions to get results = A [OK]

Hint: Always await async functions to get their results [OK]

Common Mistakes:

• Calling async functions without await
• Using sync HTTP clients in async views
• Changing async def to def incorrectly