Template filters (date, length, default) in Django - Step-by-Step Execution

Concept Flow - Template filters (date, length, default)

Start with variable

↓

Apply filter: date

↓

Apply filter: length

↓

Apply filter: default

↓

Render final output

The template engine takes a variable, applies filters one by one (date, length, default), and then shows the final result.

Execution Sample

Django

{% with my_date|date:"Y-m-d" as formatted_date %}
  {{ formatted_date|default:"No date" }}
{% endwith %}

{{ my_list|length }}

{{ my_var|default:"Default value" }}

This code formats a date, shows its length, and provides default values if variables are empty or missing.

Execution Table

Step	Variable/Input	Filter Applied	Filter Result	Output Rendered
1	my_date = 2024-06-15 14:30:00	date:"Y-m-d"	2024-06-15	No output yet
2	formatted_date = 2024-06-15	default:"No date"	2024-06-15	2024-06-15
3	my_list = [1, 2, 3, 4]	length	4	4
4	my_var = None	default:"Default value"	Default value	Default value
5	my_var = "Hello"	default:"Default value"	Hello	Hello

💡 All filters applied and outputs rendered for each variable.

Variable Tracker

Variable	Start	After date filter	After length filter	After default filter	Final Output
my_date	2024-06-15 14:30:00	2024-06-15		2024-06-15	2024-06-15
my_list	[1, 2, 3, 4]		4		4
my_var (None)	None			Default value	Default value
my_var ("Hello")	"Hello"			Hello	Hello

Key Moments - 3 Insights

Why does the default filter show "Default value" when my_var is None?

Because in the execution_table step 4, my_var is None which is treated as empty, so default filter replaces it with "Default value".

What happens if the date filter is applied to a non-date variable?

The date filter expects a date object; if given a non-date, it will output an empty string or the default if provided.

How does the length filter work on a list?

As seen in step 3, length filter counts the number of items in the list and outputs that number.

Visual Quiz - 3 Questions

Look at the execution table, what is the output after applying the default filter to my_var when it is None?

A Empty string

B Default value

C None

D my_var

💡 Hint

Check step 4 in the execution_table where my_var is None and default filter is applied.

At which step does the length filter get applied and what is the result?

A Step 3, result 4

B Step 2, result 2024-06-15

C Step 4, result Default value

D Step 1, result 2024-06-15 14:30:00

💡 Hint

Look for the step where my_list is processed with length filter.

If my_date was empty, what would the output be after applying date and default filters?

A 2024-06-15

B Empty string

C No date

D Error

💡 Hint

The default filter provides fallback text ("No date") if the date filter output is empty.

Concept Snapshot

Template filters modify variables in templates.
Use date to format dates: {{ my_date|date:"Y-m-d" }}
Use length to count items: {{ my_list|length }}
Use default to provide fallback: {{ my_var|default:"Fallback" }}
Filters apply left to right, outputting the final rendered value.

Full Transcript

In Django templates, filters change how variables appear. The date filter formats date objects into strings like '2024-06-15'. The length filter counts items in lists or strings. The default filter shows a fallback value if the variable is empty or missing. Filters apply one after another, and the final result is shown in the template. For example, if a date is missing, default can show 'No date' instead of blank. This helps templates stay clear and user-friendly.