nnA key feature of Jinja’s `for` loop is the ability to provide an **`else` block** that renders only when the loop doesn’t execute any iterations. This happens when the sequence you’re looping over is empty or when a conditional filter removes all items. The `else` block is a clean and elegant way to display a fallback message, such as “no items found,” without needing to use a separate `if/else` statement.nn

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How It Works

nUnlike Python, where an `else` block is executed if a loop completes without hitting a `break` statement, Jinja’s `else` block is specifically designed to handle cases where the loop never runs. The template engine first checks the sequence to be iterated. If the sequence is empty, the entire `for` block is skipped, and the code within the `else` block is rendered instead. This is a very predictable and reliable way to handle empty data gracefully in your templates.n

Syntax

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{% for item in sequence %}n    <!-- Code to render for each item -->n{% else %}n    <!-- Code to render if the sequence is empty -->n{% endfor %}

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Demonstration with Code Samples

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1. Handling an Empty List

nThis is the most common use case for the `else` block, where you want to display a message when a list of items is empty. The example below shows how to display a “no users found” message when the `users` list is empty.nnJinja2 Templaten

{% set users = [] %}n<ul>n{% for user in users %}n    <li>{{ user.username|e }}</li>n{% else %}n    <li><em>no users found</em></li>n{% endfor %}n</ul>

nExplanation: Since the `users` list is an empty array, the `for` loop is never entered. The Jinja engine proceeds directly to the `else` block, which then renders the “no users found” message inside a list item.nn

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2. Handling a Filtered-Out List

nThe `else` block also works perfectly with conditional filtering. If your filter removes every item from the sequence, the `else` block will be executed.nnJinja2 Templaten

{% set products = [n    {'name': 'Laptop', 'in_stock': false},n    {'name': 'Mouse', 'in_stock': false}n] %}n<ul>n{% for product in products if product.in_stock %}n    <li>{{ product.name|e }}</li>n{% else %}n    <li><em>no products currently in stock</em></li>n{% endfor %}n</ul>

nExplanation: The `for` loop with the `if product.in_stock` filter checks both items in the `products` list. Since both items have `in_stock: false`, the filter removes them, and the loop never iterates. As a result, the `else` block is executed, displaying the “no products currently in stock” message.nn