Chapter 2 - Templates

Creating Web templates.

I- Templates

A template is a file that can be used as a basis to generate files such as configuration files or source code files.

Flask uses Jinja2 as a template engine. The following code is an example of a Jinja2 template:

<ul> {% for e in employees %} <li>{{ e }}</li> {% endfor %} </ul>

Jinja2 proposes two mechanisms to help developers to generate documents:

A- Expressions

Expressions are surrounded by {{ }} and are evaluated by Jinja. The expression is then replaced by its evaluation.

The following snippet show few example of expressions:

abc{{ "def" }}ghij {{ employee }} {{ employee.name }}

B- Statements

Statements enables to control the way Jinja generates the response, such as with:

• If conditional statements

  {% if user.connected %} User is connected {% endif %}

• For control loop

  {% for user in users %} a user {% endfor %}

B- Using templates

Create a templates folder: it will contain all the templates of the application. Copy the template from Section I-A in templates/employees.html.

Let's now generate a view that uses this template. To do so, implement a view as in the following snippet:

from flask import request, url_for, redirect, session, render_template @app.route("/employees") def display_employees(): employees = ["John", "Bob", "Henry", "Alice", "Alan"] return render_template("employees.html", employees=employees)

C- Reusing code from other templates

In the templates folder, create a templates/layout.html with the following code:.

Let's now generate a view that will use this template. To do so, implement a view as in the following snippet:

Title: {% block block_title %} {% endblock %} <br/> Body: {% block body %} {% endblock %}

Now, modify the templates/employees.html, according to the following snippet:

{% extends "layout.html" %} {% block block_title %} List of employees {% endblock %} {% block body %} {% for e in employees %} <li>{{ e }}</li> {% endfor %} {% endblock %}

You should get the following result: