Template filters (date, length, default) in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django template snippet?

Given the context variable my_date with value 2024-06-15, what will this template output?

{{ my_date|date:"Y-m-d" }}

A June 15, 2024

B 06/15/2024

C 15-06-2024

D 2024-06-15

💡 Hint

The date filter formats the date according to the given string pattern.

The filter uses the format string 'Y-m-d' which means 4-digit year, dash, 2-digit month, dash, 2-digit day.

❓ state_output

intermediate

What is the length output of this list in a Django template?

Given the context variable items as ["apple", "banana", "cherry"], what does this template output?

{{ items|length }}

A 5

B 3

C 0

D Error

💡 Hint

The length filter counts the number of items in a list.

The list has three elements, so length returns 3.

📝 Syntax

advanced

Which template filter usage correctly provides a default value?

You want to display the variable username but show 'Guest' if it is empty or undefined. Which option does this correctly?

A {{ username|default_guest }}

B {{ username|default_if_none:"Guest" }}

C {{ username|default:"Guest" }}

D {{ username|default('Guest') }}

💡 Hint

The default filter replaces empty or undefined variables with the given string.

The default filter takes a string argument in quotes. default_if_none only replaces None, not empty strings.

🔧 Debug

advanced

Why does this template raise an error?

Template snippet:

{{ my_date|date:Y-m-d }}

Assuming my_date is a valid date object, why does this cause an error?

A Missing quotes around the date format string causes a syntax error

B my_date is not a date object

C The date filter does not accept format strings

D The pipe symbol is invalid here

💡 Hint

Check how the date format string is passed to the filter.

The date filter requires the format string to be quoted. Without quotes, the template parser throws an error.

🧠 Conceptual

expert

What is the output of this Django template code?

Given the context variable user_name with value None, what does this template output?

{{ user_name|default:"Anonymous"|length }}

A 9

B 0

C Error

D None

💡 Hint

The default filter replaces None with 'Anonymous', then length counts characters.

user_name is None, so default replaces it with 'Anonymous'. The length filter then counts the characters in 'Anonymous', which is 9.

Practice

1. What does the Django template filter length do when applied to a list variable?

easy

A. It returns the number of items in the list.

B. It changes the list into a string.

C. It formats the list as a date.

D. It provides a default value if the list is empty.

Solution

1. Step 1: Understand the purpose of the length filter

   The length filter counts how many items are in a list or string.

2. Step 2: Apply the filter to a list variable

   When used on a list, it returns the count of elements inside it.

3. Final Answer:

   It returns the number of items in the list. -> Option A

4. Quick Check:

   length counts items [OK]

Hint: Remember: length counts items, not changes data type [OK]

Common Mistakes:

• Thinking length changes data format
• Confusing length with default filter
• Assuming length formats dates

2. Which of the following is the correct syntax to use the default filter in a Django template to show 'N/A' if a variable user_name is empty?

easy

A. {{ user_name | default:N/A }}

B. {{ user_name | default('N/A') }}

C. {{ user_name | default:'N/A' }}

D. {{ user_name | default=N/A }}

Solution

1. Step 1: Recall the syntax for filters with arguments

   Filters use the pipe symbol and arguments are passed with a colon and quotes for strings.

2. Step 2: Identify the correct syntax for default

   The correct syntax is {{ variable | default:'value' }} using single or double quotes inside the colon.

3. Final Answer:

   {{ user_name | default:'N/A' }} -> Option C

4. Quick Check:

   Use colon and quotes for filter arguments [OK]

Hint: Use colon and quotes for filter arguments [OK]

Common Mistakes:

• Using parentheses instead of colon
• Omitting quotes around string argument
• Using equal sign instead of colon

3. Given the template code:

{{ my_date|date:"Y-m-d" }}

and my_date is a Python datetime object representing March 5, 2024, what will be the output?

medium

A. 2024-03-05

B. 03/05/2024

C. March 5, 2024

D. 05-03-2024

Solution

1. Step 1: Understand the date filter format string

   The format string "Y-m-d" means 4-digit year, dash, 2-digit month, dash, 2-digit day.

2. Step 2: Apply the format to the date March 5, 2024

   Year is 2024, month is 03, day is 05, so output is "2024-03-05".

3. Final Answer:

   2024-03-05 -> Option A

4. Quick Check:

   Date format Y-m-d = 2024-03-05 [OK]

Hint: Match format letters to date parts exactly [OK]

Common Mistakes:

• Confusing month and day order
• Ignoring leading zeros
• Using wrong format letters

4. What is wrong with this Django template code?

{{ items|length:'default' }}

Assuming items is a list variable.

medium

A. The default filter should be used instead of length.

B. The variable items must be converted to string first.

C. The colon should be replaced with a pipe symbol.

D. The length filter does not take any arguments.

Solution

1. Step 1: Check the usage of length filter

   The length filter counts items and does not accept any arguments.

2. Step 2: Identify the error in the code

   Passing 'default' as an argument with colon is invalid syntax for length.

3. Final Answer:

   The length filter does not take any arguments. -> Option D

4. Quick Check:

   length has no arguments [OK]

Hint: Remember: length filter never takes arguments [OK]

Common Mistakes:

• Trying to pass default value to length
• Confusing filter argument syntax
• Using colon incorrectly with length

5. In a Django template, you want to display the length of a list users, but if the list is empty or undefined, show 'No users'. Which template code achieves this correctly?

hard

A. {{ users|default:'No users'|length }}

B. {{ users|length|default:'No users' }}

C. {{ users|length:'No users' }}

D. {{ users|default:'No users' }} (length missing)

Solution

1. Step 1: Understand filter order and behavior

   First, length counts items in users. If users is empty or undefined, length returns 0 or errors.

2. Step 2: Use default after length to provide fallback

   Applying default:'No users' after length replaces empty or zero output with 'No users'.

3. Final Answer:

   {{ users|length|default:'No users' }} -> Option B

4. Quick Check:

   Chain length then default for fallback [OK]

Hint: Apply length first, then default for fallback text [OK]

Common Mistakes:

• Applying default before length (wrong fallback)
• Passing argument to length filter
• Omitting length filter when counting