How does the Django template language work?

Question

IT Interview Practice · Accepted Answer

The **Django Template Language (DTL)** is used to generate HTML dynamically — templates are HTML files with special syntax for inserting data, looping, and conditionals. It deliberately limits logic in templates, keeping presentation separate from business logic (which belongs in views). ## The three main syntaxes ```html

Author: {{ article.author.name }}

{% if user.is_authenticated %}

Welcome, {{ user.username }}

{% else %} Log in {% endif %} {% for article in articles %}

{% empty %}

No articles yet.

{% endfor %} {{ name|upper }} {{ article.body|truncatewords:30 }} {{ price|floatformat:2 }} {{ date|date:"Y-m-d" }} ``` Variables (`{{ }}`) output data, tags (`{% %}`) provide logic, and filters (`|`) transform values for display. ## Template inheritance — the key feature for DRY layouts ```html {% block title %}My Site{% endblock %} {% block content %}{% endblock %} ``` ```html {% extends "base.html" %} {% block title %}Articles{% endblock %} {% block content %} {% for a in articles %}

{% endfor %} {% endblock %} ``` **Template inheritance** (`{% extends %}` + `{% block %}`) lets you define a common layout once (nav, footer, structure) and have child templates fill in specific sections — avoiding repeating the page shell on every page (DRY). ## Auto-escaping protects against XSS (security) ```html {{ user_input }} {{ trusted|safe }} ``` By default, Django **auto-escapes** variable output, neutralizing HTML/script injection — a built-in **XSS protection** that you'd otherwise have to handle manually. ## Deliberately limited logic ```text DTL intentionally restricts logic (no arbitrary Python) → forces business logic into VIEWS, keeping templates focused on presentation. This separation is a feature. ``` ## Why it matters The Django template language is how you generate dynamic HTML, making it essential for any server-rendered Django application. Understanding its syntax — variables (`{{ }}`) for outputting data, tags (`{% %}`) for loops and conditionals, and filters (`|`) for formatting — is everyday knowledge for building pages. Two aspects are especially important. First, **template inheritance** (`{% extends %}` and `{% block %}`) is a powerful DRY feature that lets you define a site's common layout once and have individual pages override specific sections, avoiding the repetition and maintenance nightmare of duplicating the page shell everywhere — a foundational technique for organizing templates in real projects. Second, the **automatic HTML escaping** provides built-in **XSS protection** (a major security benefit) by neutralizing injected scripts in user data by default, something you'd have to remember to do manually in many other systems. The DTL's deliberate limitation of logic also enforces good separation of concerns by pushing business logic into views. Knowing template syntax, inheritance, auto-escaping, and the presentation/logic separation is core knowledge for building maintainable, secure server-rendered Django applications.

The three main syntaxes

Template inheritance — the key feature for DRY layouts

Auto-escaping protects against XSS (security)

Deliberately limited logic

Why it matters

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