---
name: 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
```
## 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 %}
{% for user in users %}
{{ user.username }}
{% endfor %}
{% endif %}
{# For multiple branches, elif and else can be used like in Python. #}
{% if message.status == "error" %}
{{ message.content }}
{% elif message.status == "success" %}
{{ message.content }}
{% else %}
{{ message.content }}
{% 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 #}
{% block head %}
{% block title %}{% endblock title %} - Learning Jinja
{% endblock head %}
{% block content %}{% endblock %}
{# the endblock tag doesn't need the name of the block #}
{# file: child.html.j2 #}
{% extends "base.html.j2" %}
{% block head %}
{{ super() }}
{% endblock %}
{% block title %}Home{% endblock %}
{% block content %}
Index
Welcome to my home homepage.
{% endblock %}
{# RESULT #}
Home - Learning Jinja
Index
Welcome to my home homepage.
```
### Including Content
You can include content from another template on your current template using
the `{% include "template/path" %}` tag.
```html
{# file: footer.html.j2 #}
{# file: index.html.j2 #}
...
Hi! I'm John Doe!
{% include "footer.html.j2" %}
...
{# RESULT #}
...
Hi! I'm John Doe!
...
```
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 #}
I'm the {{ name }} and i like to {{ hobby }}.
{# file: index.html.j2 #}
{% set name = "Captain Nemo" %}
{% set hobby = "navigate through the depths of the ocean" %}
{% include "greetings.html.j2" %}
{# RESULT #}
I'm the Captain Nemo and i like to navigate through the depths of the ocean.
```
## 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="") -%}
{%- endmacro %}
{{ input(placeholder="Your username") }}
{{ input(type="password") }}
```
## Official Documentation
To learn more, access the [official documentation](https://jinja.palletsprojects.com/en/).