Template inheritance with base template in Django

Introduction

Template inheritance helps you reuse common parts of your web pages easily. It saves time and keeps your code neat.

You want all pages on your website to share the same header and footer.

You need to change the look of many pages by editing just one file.

You want to keep your HTML organized by separating common layout from page content.

You are building a website with many pages that have a similar structure.

You want to avoid repeating the same HTML code in multiple templates.

Syntax

Django

{% extends "base.html" %}

{% block content %}
  <!-- Your page content here -->
{% endblock %}

Use {% extends %} at the very top of your child template to inherit from the base template.

Define {% block %} sections in your base template that child templates can fill or override.

Examples

This child template sets the page title and content inside the blocks defined in the base template.

Django

{% extends "base.html" %}

{% block title %}Home Page{% endblock %}

{% block content %}
  <p>Welcome to the home page!</p>
{% endblock %}

This child template only overrides the content block, leaving other parts from the base template unchanged.

Django

{% extends "base.html" %}

{% block content %}
  <h1>About Us</h1>
  <p>Information about our company.</p>
{% endblock %}

Sample Program

The base.html file defines the common page layout with blocks for title and content. The home.html file inherits from base.html and fills in the title and content blocks with page-specific information.

Django

{# base.html #}
<!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 Website{% endblock %}</title>
</head>
<body>
  <header>
    <h1>My Website Header</h1>
  </header>

  <main>
    {% block content %}
    <p>Default content.</p>
    {% endblock %}
  </main>

  <footer>
    <p>© 2024 My Website</p>
  </footer>
</body>
</html>


{# home.html #}
{% extends "base.html" %}

{% block title %}Home Page{% endblock %}

{% block content %}
  <p>Welcome to the home page!</p>
{% endblock %}

Important Notes

Always put {% extends %} at the very top of your child template file.

Blocks in the base template act like placeholders that child templates can fill.

If a child template does not override a block, the base template's content for that block is used.

Summary

Template inheritance lets you reuse common page parts easily.

Use {% extends %} to inherit and {% block %} to define replaceable sections.

This keeps your templates clean and easy to maintain.

Practice

1. What is the main purpose of using {% extends %} in a Django template?

easy

A. To define a new block inside the template

B. To include JavaScript files in the template

C. To inherit the layout and content from a base template

D. To load static files like images or CSS

Solution

1. Step 1: Understand the role of {% extends %}

   This tag tells Django to use another template as the base layout for the current template.

2. Step 2: Compare with other options

   Options B, C, and D describe different template tags or functions unrelated to inheritance.

3. Final Answer:

   To inherit the layout and content from a base template -> Option C

4. Quick Check:

   {% extends %} = inherit base template [OK]

Hint: Remember: extends means 'use base template' [OK]

Common Mistakes:

• Confusing extends with include
• Thinking extends loads static files
• Mixing block and extends tags

2. Which of the following is the correct syntax to define a block named 'content' in a Django template?

easy

A. {% content block %} ... {% endcontent %}

B. {% block 'content' %} ... {% endblock %}

C. {% define content %} ... {% enddefine %}

D. {% block content %} ... {% endblock %}

Solution

1. Step 1: Recall block syntax in Django templates

   The correct syntax uses {% block blockname %} and closes with {% endblock %} without quotes.

2. Step 2: Check each option

   {% block content %} ... {% endblock %} matches the correct syntax. Options A, C, and D use invalid tags. {% block 'content' %} ... {% endblock %} incorrectly uses quotes around the block name.

3. Final Answer:

   {% block content %} ... {% endblock %} -> Option D

4. Quick Check:

   Block syntax = {% block name %} ... {% endblock %} [OK]

Hint: Blocks never use quotes around their names [OK]

Common Mistakes:

• Adding quotes around block names
• Using wrong tag names like define or content block
• Forgetting to close the block with endblock

3. Given the base template

{% raw %}{% block title %}Base Title{% endblock %}{% block content %}Base Content{% endblock %}{% endraw %}

and a child template

{% raw %}{% extends 'base.html' %}{% block title %}Child Title{% endblock %}{% endraw %}

, what will be the rendered output for the content block when rendering the child template?

medium

A. Base Content

B. Child Title

C. Child Content

D. Empty content block

Solution

1. Step 1: Understand block overriding in inheritance

   The child template overrides only the title block, so the content block remains as defined in the base template.

2. Step 2: Determine output for content block

   Since the child does not override content, the base template's Base Content is used.

3. Final Answer:

   Base Content -> Option A

4. Quick Check:

   Unchanged blocks show base content [OK]

Hint: Only overridden blocks change output [OK]

Common Mistakes:

• Assuming all blocks are replaced
• Confusing title block content with content block
• Expecting empty output if block not overridden

4. Identify the error in this child template code:

{% raw %}{% extends 'base.html' %}{% block content %}Hello World{% endblock content %}{% endraw %}

medium

A. Incorrect closing tag for block; should be {% endblock %} not {% endblock content %}

B. Missing {% load static %} tag

C. The extends tag must be at the end of the file

D. Block name 'content' is invalid

Solution

1. Step 1: Check block closing syntax

   The correct way to close a block is with {% endblock %} without repeating the block name.

2. Step 2: Verify other options

   Missing {% load static %} tag is unrelated to block syntax. The extends tag must be at the end of the file is false; extends must be at the top. Block name 'content' is invalid is incorrect; 'content' is a valid block name.

3. Final Answer:

   Incorrect closing tag for block; should be {% endblock %} not {% endblock content %} -> Option A

4. Quick Check:

   Block ends with {% endblock %} only [OK]

Hint: End blocks with just {% endblock %} [OK]

Common Mistakes:

• Adding block name after endblock
• Placing extends tag incorrectly
• Confusing load static with block syntax

5. You have a base template with blocks header, content, and footer. You want a child template to reuse the base layout but add a sidebar inside the content block without losing the original content. Which is the correct way to do this?

hard

A. {% raw %}{% extends 'base.html' %}{% block sidebar %}Sidebar content{% endblock %}{% endraw %}

B. {% raw %}{% extends 'base.html' %}{% block content %}{{ block.super }}Sidebar content{% endblock %}{% endraw %}

C. {% raw %}{% extends 'base.html' %}{% block content %}Sidebar content{% endblock %}{% endraw %}

D. {% raw %}{% extends 'base.html' %}{% block content %}Sidebar content{% endblock %}{% endraw %}

Solution

1. Step 1: Understand how to keep base content in a block

   Using {{ block.super }} inside a block includes the original content from the base template's block.

2. Step 2: Analyze options

   {% raw %}{% extends 'base.html' %}{% block content %}{{ block.super }}
   Sidebar content{% endblock %}{% endraw %} correctly adds sidebar content after the original content. Options B and D replace the content entirely. {% raw %}{% extends 'base.html' %}{% block sidebar %}Sidebar content{% endblock %}{% endraw %} tries to add a new block 'sidebar' which doesn't exist in base, so it won't appear.

3. Final Answer:

   {% extends 'base.html' %}{% block content %}{{ block.super }}
   Sidebar content
   {% endblock %} -> Option B

4. Quick Check:

   Use {{ block.super }} to keep base block content [OK]

Hint: Use {{ block.super }} to keep base block content [OK]

Common Mistakes:

• Overwriting block content without block.super
• Adding blocks not defined in base template
• Forgetting to extend the base template