Jinja Templates

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Jinja Templates#

Jinja is a fast, expressive, and extensible templating engine for Python. It’s most commonly associated with Flask, but it’s also used in many other Python frameworks and applications.

Here’s what makes Jinja powerful:

  • Template inheritance: Create base templates and extend them with specific content

  • Control structures: Use if/else conditions, for loops, and macros in your templates

  • Filters: Transform values directly in templates using built-in or custom filters

  • Automatic escaping: Helps prevent XSS vulnerabilities by escaping HTML

A simple example of a Jinja template:

<!DOCTYPE html>
<html>
<head>
    <title>{{ page_title }}</title>
</head>
<body>
    <h1>Hello, {{ name }}!</h1>

    {% if items %}
        <ul>
        {% for item in items %}
            <li>{{ item }}</li>
        {% endfor %}
        </ul>
    {% else %}
        <p>No items found.</p>
    {% endif %}
</body>
</html>

When used with Flask, you’d render this template with something like:

@app.route('/')
def index():
    return render_template('index.html',
                        page_title='My App',
                        name='User',
                        items=['Item 1', 'Item 2', 'Item 3'])
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