Template fragment caching in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start caching a template fragment with the key 'sidebar'.

Django

{% [1] 'sidebar' %}

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

Acache

Bload

Cinclude

Dblock

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'load' instead of 'cache'

Trying to use 'include' for caching

Using 'block' which is for template inheritance

The cache tag is used to start caching a template fragment with a given key.

2fill in blank

medium

Complete the code to end the cache block in a Django template.

Django

{% [1]cache %}

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

Astop

Bstart

Cend

Dclose

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startcache' instead of 'endcache'

Using 'stopcache' or 'closecache' which are invalid

The cache block is closed with endcache tag, written as {% endcache %}.

3fill in blank

hard

Fix the error in the cache tag to cache a fragment for 600 seconds with key 'menu'.

Django

{% cache [1] 'menu' %}

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

Atimeout='600'

B'600'

Ctimeout=600

D600

Attempts:

3 left

💡 Hint

Common Mistakes

Putting quotes around 600

Using 'timeout=600' which is invalid syntax in template tags

The cache tag expects the timeout as an integer without quotes, so 600 is correct.

4fill in blank

hard

Fill both blanks to cache a fragment for 300 seconds with a variable key 'user.id'.

Django

{% cache [1] [2] %}

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

A300

Buser.id

C'user.id'

Duser_id

Attempts:

3 left

💡 Hint

Common Mistakes

Quoting the variable key

Using a string instead of a number for timeout

The first blank is the timeout in seconds (300). The second blank is the variable key without quotes (user.id).

5fill in blank

hard

Fill all three blanks to cache a fragment for 120 seconds with key 'product.id' and load the 'cache' template tag library.

Django

{% [1] cache %}
{% cache [2] [3] %}
Content here
{% endcache %}

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

Aload

B120

Cproduct.id

Dinclude

Attempts:

3 left

💡 Hint

Common Mistakes

Not loading the cache library

Quoting the variable key

Using 'include' instead of 'load'

First, load the cache tag library with load cache. Then use cache 120 product.id to cache for 120 seconds with the variable key.

Practice

1. What is the main purpose of using {% cache %} in Django templates?

easy

A. To permanently store user data in the database

B. To save a part of the page output and reuse it to speed up loading

C. To encrypt sensitive information in the template

D. To validate form inputs before rendering

Solution

1. Step 1: Understand what template fragment caching does

   Template fragment caching stores the rendered output of a part of a template to avoid re-rendering it every time.

2. Step 2: Identify the purpose of the {% cache %} tag

   The {% cache %} tag is used to wrap parts of a template that should be cached for faster page loads.

3. Final Answer:

   To save a part of the page output and reuse it to speed up loading -> Option B

4. Quick Check:

   Template fragment caching = save and reuse output [OK]

Hint: Cache stores parts of page output to speed loading [OK]

Common Mistakes:

• Thinking cache stores user data permanently
• Confusing cache with encryption
• Using cache tag for form validation

2. Which of the following is the correct syntax to cache a template fragment for 300 seconds with key 'sidebar'?

easy

A. {% cache 300 sidebar %} ... {% endcache %}

B. {% cache sidebar 300 %} ... {% endcache %}

C. {% cache 'sidebar' 300 %} ... {% endcache %}

D. {% cache 300 'sidebar' %} ... {% endcache %}

Solution

1. Step 1: Recall the correct order of arguments in the cache tag

   The syntax is {% cache timeout key %} where timeout is an integer and key is a string.

2. Step 2: Match the syntax with the options

   {% cache 300 'sidebar' %} ... {% endcache %} uses 300 as timeout and 'sidebar' as key in correct order and quotes.

3. Final Answer:

   {% cache 300 'sidebar' %} ... {% endcache %} -> Option D

4. Quick Check:

   Cache syntax = timeout then quoted key [OK]

Hint: Timeout first, then quoted key in cache tag [OK]

Common Mistakes:

• Putting key before timeout
• Not quoting the cache key string
• Using variable name without quotes

3. Given this template code:

{% cache 600 'menu' user.id %}

  
Home
  
Profile

{% endcache %}

What happens if user.id changes?

medium

A. A new cache entry is created for the new user.id

B. The cached fragment is reused regardless of user.id

C. The cache is cleared completely

D. An error occurs because user.id cannot be used

Solution

1. Step 1: Understand cache key with extra parameters

   Extra parameters after the key string are used to create a unique cache key per value.

2. Step 2: Effect of changing user.id on cache

   When user.id changes, Django creates a new cache entry for that user, so the fragment is cached separately.

3. Final Answer:

   A new cache entry is created for the new user.id -> Option A

4. Quick Check:

   Cache key + params = unique cache per user [OK]

Hint: Extra params create unique cache keys [OK]

Common Mistakes:

• Assuming cache ignores extra parameters
• Thinking cache clears all entries on param change
• Believing user.id cannot be used in cache tag

4. Identify the error in this template fragment caching usage:

{% cache 'sidebar' 300 %}
Sidebar content
{% endcache %}

medium

A. The timeout and key order is reversed; timeout must come first

B. Missing closing tag {% endcache %}

C. The cache key must be an integer, not a string

D. Cache tag cannot wrap HTML elements

Solution

1. Step 1: Check the order of arguments in the cache tag

   The correct order is timeout (integer) first, then cache key (string).

2. Step 2: Identify the mistake in the given code

   The code uses 'sidebar' first and 300 second, which is reversed.

3. Final Answer:

   The timeout and key order is reversed; timeout must come first -> Option A

4. Quick Check:

   Timeout first, key second in cache tag [OK]

Hint: Timeout always before key in cache tag [OK]

Common Mistakes:

• Swapping timeout and key order
• Forgetting to close cache tag
• Thinking cache tag can't wrap HTML

5. You want to cache a sidebar that shows user-specific data but also updates every 10 minutes. Which is the best way to use template fragment caching?

hard

A. Do not use cache because user data changes

B. {% cache 600 'sidebar' %} ... {% endcache %} to cache once for all users

C. {% cache 600 'sidebar' user.id %} ... {% endcache %} to cache per user for 10 minutes

D. {% cache 'sidebar' 600 user.id %} ... {% endcache %} with wrong argument order

Solution

1. Step 1: Understand caching user-specific data

   To cache user-specific content, include a unique user identifier in the cache key.

2. Step 2: Set cache timeout to 600 seconds (10 minutes)

   Use 600 seconds as timeout to update cache every 10 minutes.

3. Step 3: Verify correct syntax and usage

   {% cache 600 'sidebar' user.id %} ... {% endcache %} to cache per user for 10 minutes uses correct syntax with timeout first, key string second, and user.id as extra parameter.

4. Final Answer:

   {% cache 600 'sidebar' user.id %} ... {% endcache %} to cache per user for 10 minutes -> Option C

5. Quick Check:

   User-specific cache with timeout = {% cache 600 'sidebar' user.id %} ... {% endcache %} to cache per user for 10 minutes [OK]

Hint: Use user.id param and timeout for user-specific cache [OK]

Common Mistakes:

• Caching once for all users ignoring user.id
• Swapping timeout and key order
• Avoiding cache for user data unnecessarily