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---
language: Jinja
contributors:
- ["Adaías Magdiel", "https://github.com/AdaiasMagdiel"]
filename: learn-jinja.j2
---
## Getting Started with Jinja
Jinja is a fast, expressive, and extensible templating engine for Python
applications.
Jinja includes a lot of functionalities, such as:
- Template inheritance and inclusion;
- Defining and importing macros within templates;
- Security mechanisms to prevent XSS attacks;
- A sandboxed environment that can safely render untrusted templates;
- Extensible filters, tests, functions, and even syntax.
A Jinja template is simply a text file. Jinja doesn't require a specific
extension, but it's common to use `.j2` or `.jinja` to make it easier for
some IDEs.
There are a few kinds of delimiters. The default Jinja delimiters are configured
as follows:
- `{% ... %}` for Statements
- `{{ ... }}` for Expressions to print to the template output
- `{# ... #}` for Comments not included in the template output
```jinja
{# This is an example of a comment. #}
{#
You can use this syntax
to write multiline comments
as well.
#}
```
## VARIABLES
```jinja
{# You have the option to access variables from the context passed to the template #}
{{ foo }}
{#
Additionally, you can use a dot (.) to access attributes of a variable or
use Python syntax, using []
#}
{{ foo.bar }}
{{ foo['bar'] }}
{# Within the template, you can define variables as well #}
{% set name = "Magdiel" %}
{{ name }}
```
## Loops
```html
<h1>Members</h1>
<ul>
{% for user in users %}
<li>{{ user.username }}</li>
{% endfor %}
</ul>
<div>
{% for key, value in my_dict.items() %}
<p>{{ key }}</p> - <p>{{ value }}</p>
{% endfor %}
</div>
<div>
{% for idx, url in enumerate(urls) %}
<a href="{{ url }}">Go to url {{ idx + 1 }}</a>
{% endfor %}
</div>
```
## Conditionals
The if statement in Jinja is similar to the if statement in Python. It is
commonly used to check if a variable is defined, not empty, and not false in
its most basic form.
```html
{% if users %}
<ul>
{% for user in users %}
<li>{{ user.username }}</li>
{% endfor %}
</ul>
{% endif %}
{# For multiple branches, elif and else can be used like in Python. #}
{% if message.status == "error" %}
<p class="text-red-400">{{ message.content }}</p>
{% elif message.status == "success" %}
<p class="text-green-400">{{ message.content }}</p>
{% else %}
<p class="text-blue-400">{{ message.content }}</p>
{% endif %}
```
## Template Inheritance
One of the most powerful features of Jinja is template inheritance. You can
create a base layout with predefined blocks that you can extend in another file
and override with your own content.
```html
{# file: base.html.j2 #}
<!DOCTYPE html>
<html lang="en">
<head>
{% block head %}
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>{% block title %}{% endblock title %} - Learning Jinja</title>
{% endblock head %}
</head>
<body>
<main>
{% block content %}{% endblock %}
{# the endblock tag doesn't need the name of the block #}
</main>
</body>
</html>
{# file: child.html.j2 #}
{% extends "base.html.j2" %}
{% block head %}
{{ super() }}
<script>
console.log("There's a console.log here")
</script>
{% endblock %}
{% block title %}Home{% endblock %}
{% block content %}
<h1>Index</h1>
<p>Welcome to my home homepage.</p>
{% endblock %}
{# RESULT #}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Home - Learning Jinja</title>
<script>
console.log("There's a console.log here")
</script>
</head>
<body>
<main>
<h1>Index</h1>
<p>Welcome to my home homepage.</p>
</main>
</body>
</html>
```
### Including Content
You can include content from another template on your current template using
the `{% include "template/path" %}` tag.
```html
{# file: footer.html.j2 #}
<footer>
<p>© 2024 - John Doe</p>
</footer>
{# file: index.html.j2 #}
...
<body>
<main>
<h1>Hi! I'm John Doe!</h1>
</main>
{% include "footer.html.j2" %}
</body>
...
{# RESULT #}
...
<body>
<main>
<h1>Hi! I'm John Doe!</h1>
</main>
<footer>
<p>© 2024 - John Doe</p>
</footer>
</body>
...
```
Variables passed to the main template can also be used in the include, as the
included template has access to the context of the main template.
```html
{# file: greetings.html.j2 #}
<p>I'm the {{ name }} and i like to {{ hobby }}.</p>
{# file: index.html.j2 #}
{% set name = "Captain Nemo" %}
{% set hobby = "navigate through the depths of the ocean" %}
<div>
{% include "greetings.html.j2" %}
</div>
{# RESULT #}
<div>
<p>I'm the Captain Nemo and i like to navigate through the depths of the ocean.</p>
</div>
```
## Macros
Macros are basically like functions in another languages. You can define macros with or without arguments and reuse them in various parts of your template.
```html
{% macro input(value="", type="text", placeholder="") -%}
<input type="{{ type }}" value="{{ value }}" placeholder="{{ placeholder }}">
{%- endmacro %}
<p>{{ input(placeholder="Your username") }}</p>
<p>{{ input(type="password") }}</p>
```
## Official Documentation
To learn more, access the [official documentation](https://jinja.palletsprojects.com/en/).
|
