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Django Templates: Building Dynamic HTML with Template Language

drwxr-xr-x2026-01-215 min0 views

Django's template system separates presentation logic from business logic enabling designers and developers to work independently on HTML interfaces and Python code respectively following the Model-Template-View architectural pattern. Templates are text files containing static HTML alongside template tags, variables, and filters that generate dynamic content based on data passed from views creating personalized web pages for each user request. The Django Template Language (DTL) provides a powerful yet intentionally limited syntax preventing complex programming logic in templates maintaining clear separation between application layers while offering sufficient flexibility for common presentation requirements like loops, conditionals, and data formatting. Understanding Django templates is essential for building user interfaces as templates control what users see, how data is displayed, and how users interact with applications through forms, navigation, and content presentation. Mastering template syntax, inheritance patterns, and best practices enables creating maintainable, reusable frontend code that scales from simple websites to complex web applications with sophisticated user interfaces and dynamic content generation capabilities.

Template Syntax Fundamentals

Django template syntax uses double curly braces for variables, curly brace-percent signs for tags, and pipe characters for filters creating a clean, readable syntax distinguishable from HTML. Variables output dynamic content passed from views appearing as {{ variable_name }} and automatically HTML-escaped preventing XSS attacks unless explicitly marked safe. Template tags perform logic operations like loops, conditionals, and template inheritance using {% tag_name %} syntax with corresponding end tags for block-level tags. Filters modify variable output using pipe syntax {{ variable|filter_name }} enabling formatting, string manipulation, and data transformation directly in templates without view code modifications. Comments use {# comment text #} for single-line comments or {% comment %} {% endcomment %} for multi-line comments excluding content from rendering and output. Understanding these syntax elements enables reading and writing Django templates effectively combining static HTML structure with dynamic data presentation.

djangotemplate_syntax.html

<!-- Django template syntax examples -->

<!-- Variables: Output dynamic content -->
<h1>{{ page_title }}</h1>
<p>Welcome, {{ user.username }}!</p>
<p>Posted on {{ post.created_at }}</p>

<!-- Accessing attributes and methods -->
<p>Author: {{ post.author.get_full_name }}</p>
<p>Comments: {{ post.comments.count }}</p>

<!-- Dictionary/object access -->
<p>{{ user_data.email }}</p>
<p>{{ config.site_name }}</p>

<!-- Filters: Modify variable output -->
<p>{{ post.title|upper }}</p>  <!-- UPPERCASE -->
<p>{{ post.content|truncatewords:50 }}</p>  <!-- First 50 words -->
<p>{{ post.created_at|date:'F d, Y' }}</p>  <!-- January 18, 2026 -->
<p>{{ post.price|floatformat:2 }}</p>  <!-- 2 decimal places -->
<p>{{ post.content|linebreaks }}</p>  <!-- Convert newlines to <p> -->
<p>{{ post.slug|slugify }}</p>  <!-- Convert to slug format -->

<!-- Chaining filters -->
<p>{{ post.title|lower|truncatewords:5 }}</p>

<!-- Template tags: Logic and control flow -->
{% if user.is_authenticated %}
    <p>Welcome back, {{ user.username }}!</p>
{% else %}
    <p>Please <a href="{% url 'login' %}">log in</a></p>
{% endif %}

<!-- For loop -->
<ul>
{% for post in posts %}
    <li>{{ post.title }} - {{ post.created_at|date:'Y-m-d' }}</li>
{% empty %}
    <li>No posts available</li>
{% endfor %}
</ul>

<!-- Comments -->
{# This is a single-line comment #}

{% comment %}
This is a multi-line comment
It won't appear in the rendered output
{% endcomment %}

Template Inheritance

Template inheritance eliminates code duplication by defining base templates containing common HTML structure that child templates extend and override selectively. Base templates define blocks using {% block block_name %} tags creating placeholders that child templates fill with specific content maintaining consistent layout across pages while allowing customization. Child templates use {% extends 'base.html' %} at the beginning followed by {% block %} tags overriding specific sections from the parent template. Multiple inheritance levels enable creating hierarchical template structures with site-wide base templates, section-specific intermediate templates, and page-specific child templates promoting maximum code reuse. This pattern mirrors object-oriented inheritance concepts applied to HTML templates enabling maintainable frontend architectures where common elements like headers, footers, and navigation appear in base templates while unique page content lives in child templates. Understanding template inheritance dramatically reduces HTML duplication, simplifies site-wide design changes requiring modifications in only base templates, and establishes professional Django development patterns used across the ecosystem.

djangotemplate_inheritance.html

<!-- base.html - Base template -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>{% block title %}My Site{% endblock %}</title>
    {% load static %}
    <link rel="stylesheet" href="{% static 'css/style.css' %}">
    {% block extra_css %}{% endblock %}
</head>
<body>
    <header>
        <nav>
            <a href="{% url 'home' %}">Home</a>
            <a href="{% url 'blog:post_list' %}">Blog</a>
            <a href="{% url 'contact' %}">Contact</a>
        </nav>
    </header>
    
    <main>
        {% block content %}
        <!-- Child templates override this block -->
        {% endblock %}
    </main>
    
    <footer>
        <p>&copy; 2026 My Site. All rights reserved.</p>
        {% block footer %}{% endblock %}
    </footer>
    
    <script src="{% static 'js/main.js' %}"></script>
    {% block extra_js %}{% endblock %}
</body>
</html>

<!-- post_list.html - Child template -->
{% extends 'base.html' %}

{% block title %}Blog Posts - {{ block.super }}{% endblock %}

{% block content %}
<h1>Blog Posts</h1>
<div class="posts-grid">
    {% for post in posts %}
    <article class="post-card">
        <h2><a href="{% url 'blog:post_detail' slug=post.slug %}">{{ post.title }}</a></h2>
        <p>{{ post.excerpt }}</p>
        <p class="meta">By {{ post.author }} on {{ post.created_at|date:'F d, Y' }}</p>
    </article>
    {% endfor %}
</div>
{% endblock %}

{% block extra_css %}
<style>
    .posts-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
</style>
{% endblock %}

<!-- post_detail.html - Another child template -->
{% extends 'base.html' %}

{% block title %}{{ post.title }} - {{ block.super }}{% endblock %}

{% block content %}
<article class="post-detail">
    <h1>{{ post.title }}</h1>
    <p class="meta">By {{ post.author.get_full_name }} | {{ post.created_at|date:'F d, Y' }} | {{ post.views }} views</p>
    <div class="post-content">
        {{ post.content|linebreaks }}
    </div>
</article>
{% endblock %}

Common Template Tags

Django provides numerous built-in template tags handling common presentation requirements from URL generation to data iteration and conditional rendering. The {% url %} tag generates URLs from view names supporting Django's URL reversing mechanism preventing hardcoded paths in templates. The {% static %} tag generates URLs for static files like CSS, JavaScript, and images automatically using the STATIC_URL setting. The {% load %} tag imports template tag libraries enabling custom tags and filters in templates. Conditional tags like {% if %}, {% elif %}, and {% else %} implement conditional rendering based on context variables, user authentication, or permissions. Loop tags like {% for %} iterate over querysets, lists, or dictionaries with {% empty %} handling empty collections gracefully. The {% csrf_token %} tag provides CSRF protection for forms inserting security tokens preventing cross-site request forgery attacks. Understanding these tags enables building sophisticated templates handling common web development patterns without writing custom tag libraries for basic functionality.

djangotemplate_tags.html

<!-- Common Django template tags -->

<!-- URL tag: Generate URLs -->
<a href="{% url 'blog:post_list' %}">All Posts</a>
<a href="{% url 'blog:post_detail' slug=post.slug %}">{{ post.title }}</a>
<a href="{% url 'blog:category' slug='technology' %}">Technology</a>

<!-- Static tag: Load static files -->
{% load static %}
<link rel="stylesheet" href="{% static 'css/style.css' %}">
<script src="{% static 'js/app.js' %}"></script>
<img src="{% static 'images/logo.png' %}" alt="Logo">

<!-- If conditions -->
{% if user.is_authenticated %}
    <p>Welcome, {{ user.username }}!</p>
    {% if user.is_staff %}
        <a href="{% url 'admin:index' %}">Admin Panel</a>
    {% endif %}
{% else %}
    <a href="{% url 'login' %}">Login</a>
{% endif %}

<!-- If with operators -->
{% if posts.count > 0 %}
    <p>Showing {{ posts.count }} posts</p>
{% endif %}

{% if user.is_authenticated and user.is_staff %}
    <button>Delete Post</button>
{% endif %}

<!-- For loop -->
<ul>
{% for post in posts %}
    <li>
        <h3>{{ post.title }}</h3>
        <p>{{ forloop.counter }}. Posted by {{ post.author }}</p>
    </li>
{% empty %}
    <li>No posts found</li>
{% endfor %}
</ul>

<!-- For loop variables -->
{% for item in items %}
    {% if forloop.first %}<div class="first">{% endif %}
    {{ forloop.counter }}: {{ item.name }}
    {% if forloop.last %}</div>{% endif %}
{% endfor %}

<!-- With tag: Create context variable -->
{% with total=posts.count %}
    <p>Total posts: {{ total }}</p>
    <p>Average: {{ total|floatformat:2 }}</p>
{% endwith %}

<!-- Now tag: Current datetime -->
<p>Generated: {% now 'Y-m-d H:i:s' %}</p>

<!-- CSRF token for forms -->
<form method="post">
    {% csrf_token %}
    <input type="text" name="title">
    <button type="submit">Submit</button>
</form>

<!-- Include tag: Include other templates -->
{% include 'partials/header.html' %}
{% include 'partials/sidebar.html' with user=request.user %}

<!-- Cycle tag: Alternate values -->
<table>
{% for row in data %}
    <tr class="{% cycle 'odd' 'even' %}">
        <td>{{ row.name }}</td>
    </tr>
{% endfor %}
</table>

Template Filters

Django template filters transform variable output directly in templates providing formatting, string manipulation, and data conversion capabilities without requiring view code changes. Filters apply using pipe syntax {{ variable|filter_name }} with optional arguments separated by colons like {{ text|truncatewords:30 }}. Common string filters include upper, lower, title for case conversion, truncatewords and truncatechars for length limiting, and linebreaks for converting newlines to HTML paragraphs. Number filters include floatformat for decimal formatting, add for arithmetic, and filesizeformat for human-readable file sizes. Date filters format datetime objects using strftime format codes like {{ date|date:'Y-m-d' }} or named formats like 'SHORT_DATE_FORMAT'. Logic filters like default provide fallback values for empty variables while yesno converts boolean values to custom strings. Understanding filters enables clean template code handling common formatting needs inline without cluttering views with presentation logic, maintaining Django's separation of concerns philosophy where views handle business logic and templates handle presentation formatting.

djangotemplate_filters.html

<!-- Django template filters -->

<!-- String filters -->
<p>{{ post.title|upper }}</p>  <!-- UPPERCASE -->
<p>{{ post.title|lower }}</p>  <!-- lowercase -->
<p>{{ post.title|title }}</p>  <!-- Title Case -->
<p>{{ post.title|capfirst }}</p>  <!-- Capitalize first letter -->

<!-- Truncation -->
<p>{{ post.content|truncatewords:50 }}</p>  <!-- First 50 words -->
<p>{{ post.title|truncatechars:30 }}</p>  <!-- First 30 characters -->
<p>{{ post.description|wordwrap:40 }}</p>  <!-- Wrap at 40 characters -->

<!-- Text formatting -->
<p>{{ post.content|linebreaks }}</p>  <!-- Convert \n to <p> -->
<p>{{ post.content|linebreaksbr }}</p>  <!-- Convert \n to <br> -->
<p>{{ user_input|safe }}</p>  <!-- Mark as safe HTML (use carefully!) -->
<p>{{ html_content|striptags }}</p>  <!-- Remove HTML tags -->

<!-- Date and time -->
<p>{{ post.created_at|date:'Y-m-d' }}</p>  <!-- 2026-01-18 -->
<p>{{ post.created_at|date:'F d, Y' }}</p>  <!-- January 18, 2026 -->
<p>{{ post.created_at|time:'H:i' }}</p>  <!-- 19:30 -->
<p>{{ post.created_at|timesince }}</p>  <!-- "2 hours ago" -->
<p>{{ post.created_at|timeuntil }}</p>  <!-- "in 3 days" -->

<!-- Numbers -->
<p>${{ product.price|floatformat:2 }}</p>  <!-- 19.99 -->
<p>{{ value|add:'5' }}</p>  <!-- Add 5 to value -->
<p>{{ file.size|filesizeformat }}</p>  <!-- "1.4 MB" -->

<!-- Lists and sequences -->
<p>{{ names|join:', ' }}</p>  <!-- Join list with comma -->
<p>Items: {{ items|length }}</p>  <!-- Count items -->
<p>{{ my_list|first }}</p>  <!-- First item -->
<p>{{ my_list|last }}</p>  <!-- Last item -->
<p>{{ my_list|slice:':5' }}</p>  <!-- First 5 items -->

<!-- Default values -->
<p>{{ optional_field|default:'Not available' }}</p>
<p>{{ empty_string|default_if_none:'N/A' }}</p>

<!-- Boolean -->
<p>{{ is_published|yesno:'Yes,No,Maybe' }}</p>

<!-- URL encoding -->
<a href="?search={{ query|urlencode }}">Search</a>

<!-- Chaining multiple filters -->
<p>{{ post.title|lower|truncatewords:10|capfirst }}</p>
<p>{{ post.created_at|date:'Y-m-d'|default:'Unknown' }}</p>

<!-- Custom display -->
<p>{{ post.content|wordcount }} words</p>
<p>{{ text|pluralize }}</p>  <!-- Add 's' if plural -->
<p>{{ count }} item{{ count|pluralize }}</p>  <!-- "1 item" or "2 items" -->
<p>{{ count }} {{ count|pluralize:'item,items' }}</p>

Template Context and Variables

Template context represents the dictionary of variables passed from views to templates making data available for rendering. Views pass context using the render() shortcut or explicitly creating Context objects containing key-value pairs where keys become template variable names. Django automatically adds context processors to every template providing common variables like request, user, and messages without explicit passing from views. Custom context processors can inject site-wide variables like configuration settings, navigation menus, or footer content into all templates maintaining DRY principles. Context variables can be simple types like strings and numbers, complex objects like model instances with accessible attributes and methods, querysets supporting iteration, or dictionaries and lists enabling nested data access. Understanding context enables efficient data flow from views to templates, accessing related data through model relationships, and leveraging Django's context processor system for application-wide template data avoiding repetitive context building in every view function.

pythontemplate_context.py

# views.py - Passing context to templates
from django.shortcuts import render
from .models import Post, Category

def post_list(request):
    # Create context dictionary
    posts = Post.objects.filter(status='published')
    categories = Category.objects.all()
    
    context = {
        'posts': posts,
        'categories': categories,
        'page_title': 'Blog Posts',
        'total_count': posts.count(),
    }
    
    return render(request, 'blog/post_list.html', context)

def post_detail(request, slug):
    post = get_object_or_404(Post, slug=slug)
    related_posts = Post.objects.filter(
        category=post.category
    ).exclude(id=post.id)[:3]
    
    context = {
        'post': post,
        'related_posts': related_posts,
        'can_edit': request.user == post.author,
    }
    
    return render(request, 'blog/post_detail.html', context)

# settings.py - Context processors
TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [BASE_DIR / 'templates'],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',  # Adds 'request'
                'django.contrib.auth.context_processors.auth',  # Adds 'user'
                'django.contrib.messages.context_processors.messages',
                # Custom context processor
                'myapp.context_processors.site_settings',
            ],
        },
    },
]

# myapp/context_processors.py - Custom context processor
def site_settings(request):
    """Add site-wide variables to all templates"""
    return {
        'SITE_NAME': 'My Django Site',
        'SITE_VERSION': '1.0',
        'FOOTER_YEAR': 2026,
    }

# In templates, access context variables:
# {{ posts }}  - From view context
# {{ request.user }}  - From request context processor
# {{ SITE_NAME }}  - From custom context processor

Creating Custom Template Tags

Django allows creating custom template tags extending template functionality beyond built-in tags enabling project-specific requirements and reusable template logic. Custom tags are defined in templatetags directory within Django apps containing Python modules registered using the Library() decorator system. Simple tags return strings or rendered content while inclusion tags render sub-templates with context, and assignment tags store results in template variables for later use. Creating custom tags involves defining a Python function decorated with appropriate Library method like @register.simple_tag or @register.inclusion_tag specifying tag behavior. Custom tags access template context, accept arguments, and perform complex logic like database queries, API calls, or calculations unavailable in template filters. Understanding custom tags enables extending Django's template system with project-specific functionality while maintaining clean template code and promoting code reuse across templates. Examples include custom pagination tags, social media share buttons, dynamic widget rendering, or complex data aggregation presenting results in templates without cluttering views with presentation logic.

pythoncustom_tags.py

# blog/templatetags/blog_tags.py - Custom template tags
from django import template
from django.db.models import Count
from blog.models import Post

register = template.Library()

# Simple tag: Returns a value
@register.simple_tag
def total_posts():
    return Post.objects.filter(status='published').count()

@register.simple_tag
def get_popular_posts(count=5):
    return Post.objects.filter(status='published').order_by('-views')[:count]

# Usage in template:
# {% load blog_tags %}
# <p>Total posts: {% total_posts %}</p>

# Inclusion tag: Renders a template
@register.inclusion_tag('blog/partials/recent_posts.html')
def show_recent_posts(count=5):
    posts = Post.objects.filter(status='published').order_by('-created_at')[:count]
    return {'posts': posts}

# blog/templates/blog/partials/recent_posts.html
# <div class="recent-posts">
#     <h3>Recent Posts</h3>
#     <ul>
#     {% for post in posts %}
#         <li><a href="{% url 'blog:post_detail' slug=post.slug %}">{{ post.title }}</a></li>
#     {% endfor %}
#     </ul>
# </div>

# Usage in template:
# {% load blog_tags %}
# {% show_recent_posts 10 %}

# Assignment tag: Stores result in variable
@register.simple_tag
def get_categories():
    return Category.objects.annotate(post_count=Count('post')).filter(post_count__gt=0)

# Usage:
# {% load blog_tags %}
# {% get_categories as categories %}
# {% for category in categories %}
#     <a href="{% url 'blog:category' slug=category.slug %}">{{ category.name }} ({{ category.post_count }})</a>
# {% endfor %}

# Tag with takes_context
@register.simple_tag(takes_context=True)
def is_author(context, post):
    request = context['request']
    return request.user == post.author

# Custom filter
@register.filter(name='reading_time')
def reading_time(text):
    word_count = len(text.split())
    minutes = word_count // 200  # Average reading speed
    return f"{minutes} min read" if minutes > 0 else "< 1 min read"

# Usage:
# {{ post.content|reading_time }}

Template Best Practices

Effective template development follows established patterns promoting maintainability, performance, and security. Use template inheritance extensively creating base templates for common layouts minimizing HTML duplication across pages and simplifying site-wide design changes. Keep templates focused on presentation avoiding complex business logic that belongs in views or models maintaining clear separation of concerns. Use template fragments and includes for reusable components like headers, footers, or form widgets promoting DRY principles. Leverage context processors for site-wide variables avoiding repetitive context creation in views. Always use {% csrf_token %} in forms protecting against cross-site request forgery attacks. Be cautious with the safe filter ensuring user-generated content is properly escaped preventing XSS vulnerabilities unless explicitly trusted. Use {% static %} tag for static files enabling proper static file management during development and production deployment. Organize templates in app-specific directories following Django's template namespacing conventions preventing name conflicts. Comment complex template logic explaining non-obvious conditionals or loops aiding future maintenance. These practices result in secure, maintainable templates that scale gracefully as applications grow in complexity.