Django Template Tags

A template tag is a special Django instruction used inside an HTML template. It allows the template to perform an operation or control how content is displayed.

{% if user %}
    <p>Welcome</p>
{% endif %}

Template tags use curly braces with percentage symbols.

{% tag %}

For example:

{% if age >= 18 %}

The closing tag for block tags is usually written separately.

Variable:

{{ name }}

Template tag:

{% if name %}

Variables generally display values, while template tags perform template operations.

The if tag is used to display content when a condition is true.

{% if age >= 18 %}
    <p>You are eligible.</p>
{% endif %}

The else section can be used when the if condition is false.

{% if age >= 18 %}
    <p>Adult</p>
{% else %}
    <p>Minor</p>
{% endif %}

Django supports elif for checking multiple conditions.

{% if marks >= 80 %}
    <p>Grade A</p>
{% elif marks >= 60 %}
    <p>Grade B</p>
{% else %}
    <p>Grade C</p>
{% endif %}

The for tag is used to repeat HTML content for each item in a collection.

{% for student in students %}
    <p>{{ student }}</p>
{% endfor %}

View:

def students(request):

    data = {
        'students': [
            'Rahul',
            'Amit',
            'Priya'
        ]
    }

    return render(
        request,
        'students.html',
        data
    )

Template:

{% for student in students %}
    <p>{{ student }}</p>
{% endfor %}

The empty clause can display a message when a collection contains no items.

{% for student in students %}
    <p>{{ student.name }}</p>
{% empty %}
    <p>No students found.</p>
{% endfor %}

The comment tag can be used for template comments that should not appear in the rendered HTML.

{% comment %}
This content is a Django template comment.
{% endcomment %}

The extends tag is used for template inheritance.

{% extends 'base.html' %}

It allows a child template to reuse the structure of a base template.

The block tag defines an area that child templates can replace.

{% block content %}

{% endblock %}

It is commonly used together with extends.

base.html

<html>
<body>

<h1>My Website</h1>

{% block content %}
{% endblock %}

</body>
</html>

home.html

{% extends 'base.html' %}

{% block content %}
    <h2>Home Page</h2>
{% endblock %}

The include tag allows one template to include another template.

{% include 'header.html' %}

This is useful for reusable components such as headers, menus, and footers.

<body>

{% include 'header.html' %}

<h1>Home Page</h1>

{% include 'footer.html' %}

</body>

Common page sections can be maintained in separate files.

The load tag is used to load template tag libraries.

For example, Django's static template tags can be loaded using:

{% load static %}

The static tag is used to generate URLs for static files.

{% load static %}

<link rel="stylesheet"
      href="{% static 'css/style.css' %}">

The csrf_token tag is commonly used inside Django POST forms to include a CSRF token.

<form method="post">

    {% csrf_token %}

    <input type="text" name="name">

    <button type="submit">Submit</button>

</form>

The url tag can create a URL using the name of a URL pattern.

{% url 'home' %}

This is useful because templates do not need to hard-code every application URL.

The url tag can also pass parameters to a named URL.

{% url 'student' student.id %}

This can generate a dynamic URL for a particular student.

The with tag creates a simpler variable name for a value inside a specific template block.

{% with full_name=student.name %}
    <h2>{{ full_name }}</h2>
{% endwith %}

The firstof tag outputs the first variable from a list of variables that evaluates to a non-empty value.

{% firstof username nickname "Guest" %}

If username is empty, Django checks the next value.

The cycle tag cycles through a list of values each time it is used inside a loop.

{% for student in students %}

    {% cycle 'one' 'two' %}

    {{ student.name }}

{% endfor %}

Django provides special variables while executing a for loop.

{% for student in students %}

    {{ forloop.counter }}.
    {{ student.name }}

{% endfor %}

forloop.counter starts counting from 1.

The forloop.counter0 variable starts counting from 0.

{% for student in students %}

    {{ forloop.counter0 }} - {{ student.name }}

{% endfor %}

This can be useful when zero-based numbering is required.

Django provides forloop.first and forloop.last to identify the first and last iteration of a loop.

{% for student in students %}

    {% if forloop.first %}
        <p>First Student</p>
    {% endif %}

    <p>{{ student.name }}</p>

    {% if forloop.last %}
        <p>Last Student</p>
    {% endif %}

{% endfor %}

Multiple template tags can be combined to create dynamic pages.

{% if students %}

    {% for student in students %}

        <p>
            {{ forloop.counter }}.
            {{ student.name }}
        </p>

    {% endfor %}

{% else %}

    <p>No students found.</p>

{% endif %}

• Using {{ }} when a template tag is required
• Forgetting to close if blocks with {% endif %}
• Forgetting {% endfor %}
• Using an incorrect tag name
• Forgetting {% load static %} when using static template tags
• Incorrect URL name with the url tag
• Incorrect template inheritance syntax

views.py

from django.shortcuts import render

def students(request):

    data = {
        'students': [
            {'name': 'Rahul', 'age': 20},
            {'name': 'Amit', 'age': 22},
            {'name': 'Priya', 'age': 21}
        ]
    }

    return render(
        request,
        'students.html',
        data
    )

students.html

<h1>Student List</h1>

{% if students %}

    {% for student in students %}

        <p>
            {{ forloop.counter }}.
            {{ student.name }}
            - {{ student.age }}
        </p>

    {% endfor %}

{% else %}

    <p>No students found.</p>

{% endif %}

Django template tags provide a way to add logic and special operations to HTML templates without placing Python code directly inside the HTML.

• if checks conditions.
• for repeats content.
• extends supports template inheritance.
• block defines replaceable sections.
• include reuses another template.
• load loads template tag libraries.
• static handles static file URLs.
• csrf_token is used with Django POST forms.
• url creates URLs from named URL patterns.
• with, firstof, and cycle provide additional template functionality.