42 Jinja2: Syntax
42.1 Basic Syntax
42.1.1 Variables
{{ variable }}
{{ user.name }}
{{ user['name'] }}
{{ user.get('name', 'default') }}42.1.3 Statements
{% statement %}42.2 Control Structures
42.2.1 If Statements
{% if condition %}
Content if condition is true
{% elif another_condition %}
Content if another_condition is true
{% else %}
Content if all conditions are false
{% endif %}42.2.2 For Loops
{% for item in items %}
{{ item }}
{% endfor %}
{% for key, value in dictionary.items() %}
{{ key }}: {{ value }}
{% endfor %}
{% for item in items %}
{{ loop.index }} {# 1-based index #}
{{ loop.index0 }} {# 0-based index #}
{{ loop.first }} {# True if first iteration #}
{{ loop.last }} {# True if last iteration #}
{{ loop.length }} {# Total number of items #}
{% else %}
No items found
{% endfor %}42.3 Template Inheritance
42.3.1 Base Template
{# base.html #}
<!DOCTYPE html>
<html>
<head>
<title>{% block title %}Default Title{% endblock %}</title>
</head>
<body>
<header>{% block header %}Default Header{% endblock %}</header>
<main>{% block content %}{% endblock %}</main>
<footer>{% block footer %}Default Footer{% endblock %}</footer>
</body>
</html>42.3.2 Child Template
{# child.html #}
{% extends "base.html" %}
{% block title %}Page Title{% endblock %}
{% block content %}
<h1>Page Content</h1>
<p>This replaces the content block from the parent template</p>
{# Include parent block content #}
{{ super() }}
{% endblock %}42.4 Includes and Imports
42.4.1 Include
{% include 'header.html' %}
{% include 'sidebar.html' ignore missing %}42.4.2 Import
{% import 'macros.html' as macros %}
{{ macros.input('username') }}
{% from 'macros.html' import input %}
{{ input('username') }}42.5 Macros (Reusable Template Functions)
42.5.1 Define Macro
{% macro input(name, value='', type='text') %}
<input type="{{ type }}" name="{{ name }}" value="{{ value }}">
{% endmacro %}42.5.2 Use Macro
{{ input('username') }}
{{ input('password', type='password') }}42.6 Filters
42.6.1 String Filters
{{ name|capitalize }} {# First letter capitalized #}
{{ name|upper }} {# All uppercase #}
{{ name|lower }} {# All lowercase #}
{{ name|title }} {# Title Case #}
{{ name|trim }} {# Remove whitespace from both ends #}
{{ name|replace('old', 'new') }} {# Replace text #}
{{ name|truncate(50) }} {# Truncate to 50 chars #}42.6.2 List Filters
{{ list|join(', ') }} {# Join list items #}
{{ list|first }} {# First item #}
{{ list|last }} {# Last item #}
{{ list|length }} {# Number of items #}
{{ list|sort }} {# Sort items #}
{{ list|reverse }} {# Reverse order #}42.6.3 Custom Filters (Python Side)
def date_filter(value, format='%Y-%m-%d'):
return value.strftime(format)
env.filters['date'] = date_filter{{ post.date|date }}
{{ post.date|date('%B %d, %Y') }}42.7 Tests
{% if variable is defined %}
{% if number is divisibleby(3) %}
{% if value is none %}
{% if string is upper %}Common tests:
defined,undefinednone,sameas(other)odd,even,divisibleby(number)string,number,iterable,mapping
42.8 Whitespace Control
{%- if condition -%} {# Remove whitespace on both sides #}
Content
{%- endif -%}
{{- variable -}} {# Remove whitespace on both sides #}42.9 Set & Block Variables
{% set name = 'John' %}
{% set users = [1, 2, 3] %}
{% set users = users + [4, 5] %}
{% set navigation %}
<li><a href="/">Home</a></li>
<li><a href="/about">About</a></li>
{% endset %}42.10 Raw Content (No Processing)
{% raw %}
This {{ will not }} be processed by Jinja2
{% endraw %}42.11 Extensions & Advanced Features
42.11.1 Expression Statement
{% do users.append('john') %} {# Do something without output #}42.11.2 With Statement
{% with foo = 42 %}
{{ foo }} {# foo is 42 here #}
{% endwith %}42.11.3 Assignments
{% set users = ['John', 'Jane'] %}42.11.4 Line Statements
# for item in items
{{ item }}
# endfor42.11.5 Template Context (Python Side)
template.render(
title="My Page",
users=["John", "Jane"],
is_admin=True
)42.12 Error Handling
{{ missing_variable|default('default value') }}This cheat sheet covers the most commonly used Jinja2 syntax elements and features. Keep it handy as you build your templates!
42.1.2 Comments