Primer on Jinja Templating

Jinja is a powerful template engine commonly used in Python web applications to create dynamic web pages. Jinja also supports standalone usage, enabling you to create text files with programmatically filled content, making it versatile beyond web frameworks like Flask and Django.

In this tutorial, you’ll learn how to install Jinja, create and render Jinja templates, and use Jinja’s features such as conditional statements and loops. You’ll also explore how to use filters and macros to enhance your templates’ functionality, and discover how to nest templates and integrate Jinja seamlessly into a Flask web application.

By the end of this tutorial, you’ll understand that:

• Jinja is used to create dynamic web templates and generate text files with programmatic content.


• A templating engine processes templates with dynamic content, rendering them as static pages.


• You use Jinja templates in HTML by embedding dynamic placeholders and rendering them with Python.


• You create an if-else statement in Jinja using {% if condition %} ... {% else %} ... {% endif %}.


• You create a for loop in Jinja using {% for item in list %} ... {% endfor %}.


• Jinja is primarily used in Python but can be integrated with other languages and frameworks.

You’ll start by using Jinja on its own to cover the basics of Jinja templating.
Later you’ll build a basic Flask web project with two pages and a navigation bar to leverage the full potential of Jinja.

Throughout the tutorial, you’ll build an example app that showcases some of Jinja’s wide range of features. To see what it’ll do, skip ahead to the final section.

You can also find the full source code of the web project by clicking on the link below:

Get Started With Jinja

Jinja is not only a city in the Eastern Region of Uganda and a Japanese temple, but also a template engine.
You commonly use template engines for web templates that receive dynamic content from the back end and render it as a static page in the front end.

But you can use Jinja without a web framework running in the background.
That’s exactly what you’ll do in this section.
Specifically, you’ll install Jinja and build your first templates.

Install Jinja

Before exploring any new package, it’s a good idea to create and activate a virtual environment.
That way, you’re installing any project dependencies in your project’s virtual environment instead of system-wide.

Select your operating system below and use your platform-specific command to set up a virtual environment:

• 
  Windows
  
• 
  Linux + macOS
  

PS> python -m venv venv

PS> .\venv\Scripts\activate

(venv) PS>

$ python -m venv venv

$ source venv/bin/activate

(venv) $

With the above commands, you create and activate a virtual environment named venv by using Python’s built-in venv module.
The parentheses (()) surrounding venv in front of the prompt indicate that you’ve successfully activated the virtual environment.

After you’ve created and activated your virtual environment, it’s time to install Jinja with pip:

(venv) $ python -m pip install Jinja2

Don’t forget the 2 at the end of the package name.
Otherwise, you’ll install an old version that isn’t compatible with Python 3.

It’s worth noting that although the current major version is actually greater than 2, the package that you’ll install is nevertheless called Jinja2.
You can verify that you’ve installed a modern version of Jinja by running pip list:

(venv) $ python -m pip list

Package    Version

---------- -------

Jinja2     3.x

...

To make things even more confusing, after installing Jinja with an uppercase J, you have to import it with a lowercase j in Python.
Try it out by opening the interactive Python interpreter and running the following commands:

>>> import Jinja2

Traceback (most recent call last):

  ...

ModuleNotFoundError: No module named 'Jinja2'


>>> import jinja2

>>> # No error