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Updated on 2024-10-28

An in-depth analysis of python's jinja2 template

The purpose of this article is to explain the knowledge related to teaching Python templates, which includes basic concepts, syntax and applications. If you don't know much about Python templates, we recommend you to read this article carefully, we will analyze Python templates for you in depth.

I. Basic concepts

Python templates, known as "Jinja2 Template", is a template engine in the Python language. In web applications, templates are generally used to generate pages or other output formats.Python's template engine provides programmers with a very convenient way to build dynamic content, enforce code structure, and allow specific information to be extracted from data.

Jinja2 is very popular in the Python community and its main features include:

  • Extensibility:Templates can include user-defined filters, global variables, tests, and more.
  • Separation of code and templates : In writing Jinja2 templates , we only need to focus on the template presentation , and do not have to care about how to show the code in the template to build .
  • Fluid Templates:Jinja2 templates are very fluid and can be easily embedded with data and code. This makes the template very easy to read and write .

II. Grammar

The Jinja2 syntax is composed of {% %}, {{ }} and {# #}. Among them:

  • {% %} is used for statements such as if statements and for statements.
  • {{ }} is used for expressions such as variables and function calls.
  • {# #} is used for comments and can be used to add comment information to the code.

Here are some examples showing some basic usage of the Jinja2 syntax:

<!DOCTYPE html>
<html>
  <head>
    <title>{{ title }}</title>
  </head>
  <body>
    <h1>{% if user %}Hello {{ user }}!{% else %}Hello World!{% endif %}</h1>
    <ul>
    {% for post in posts %}
      <li><a href="{{  }}" rel="external nofollow" >{{  }}</a></li>
    {% endfor %}
    </ul>
  </body>
</html>

In templates, we can use variables, filters, loops, etc.

1. Variables

In Jinja2, we can use {{ }} to get the value of a variable. For example, we can write the following code:

{% set name = 'Alice' %}
My name is {{ name }}.

This code will output "My name is Alice.".

2. Filter

We can use filters in {{ }} to manipulate variables. For example, we can use the capitalize filter to change the first letter of a variable to uppercase:

{{ 'hello python' | capitalize }}

This code will output "Hello python".

3. Loop statements

Loop statements in Jinja2 are similar to for loop statements in Python. For example, we can use the following code to output all the elements in a list:

{% for item in items %}
  {{ item }}
{% endfor %}

III. Applications

Python templates are widely used in web applications such as Flask, Django, etc. Here is a simple example showing how to use Jinja2 templates in a Flask application:

from flask import Flask, render_template

app = Flask(__name__)

@('/')
def index():
    return render_template('', title='Home')

if __name__ == '__main__':
    (debug=True)

In the application, we can call the render_template function to render the template. For example, we can use the following code:

<!DOCTYPE html>
<html>
  <head>
    <title>{{ title }}</title>
  </head>
  <body>
    <h1>Hello World!</h1>
  </body>
</html>

In a Flask application, we can use the following command to start the application:

$ export FLASK_APP=
$ flask run

IV. Summary

This article introduces Python templating instruction in terms of basic concepts, syntax, and applications.The Jinja2 template engine is a powerful and flexible templating system that can be used to generate output in a variety of formats. In web applications, the Jinja2 template engine is tightly coupled with frameworks such as Flask and Django, and they can help you create dynamic applications more efficiently.

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