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Flask Framework Cookbook
Flask Framework Cookbook

Flask Framework Cookbook: Over 80 proven recipes and techniques for Python web development with Flask , Second Edition

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Flask Framework Cookbook

Templating with Jinja2

This chapter will cover the basics of Jinja2 templating from the perspective of Flask; we will also learn how to make applications with modular and extensible templates.

In Flask, we can write a complete web application without the need for third-party templating engine. For example, have a look at the following code; this is a standalone, simple Hello World application with a bit of HTML styling included:

from flask import Flask 
app = Flask(__name__) 
 
@app.route('/') 
@app.route('/hello') 
@app.route('/hello/<user>') 
def hello_world(user=None): 
    user = user or 'Shalabh' 
    return ''' 
<html> 
    <head> 
      <title>Flask Framework Cookbook</title> 
 
    </head> 
      <body> 
        <h1>Hello %s!</h1> 
        <p>Welcome to the...

Bootstrapping the recommended layout

Most of the applications in Flask follow a specific pattern of laying out templates. In this recipe, we will implement the recommended way of structuring the layout of templates in a Flask application.

Getting ready

By default, Flask expects templates to be placed inside a folder named templates at the application root level. If this folder is present, then Flask will automatically read the contents by making the contents of this folder available for use with the render_template() method, which we will use extensively throughout this book.

How to do it...

...

Implementing block composition and layout inheritance

Usually, any web application will have a number of web pages that are different to each other. However, code blocks such as headers and footers will appear the same on almost all pages throughout the site; likewise, the menu will remain the same. In fact, it is usually just the center container block that changes. For this, Jinja2 provides a great way of ensuring inheritance among templates.

With this in mind, it's good practice to have a base template where the basic layout of the site, along with the header and footer, can be structured.

Getting ready

In this recipe, we will try to create a small application where we will have a home page and a product page (such...

Creating a custom context processor

Sometimes, we might want to calculate or process a value directly in templates. Jinja2 maintains the notion that the processing of logic should be handled in views and not in templates, and so keeps templates clean. A context processor becomes a handy tool in this case. With a context processor, we can pass our values to a method, which will then be processed in a Python method, and our resultant value will be returned. This is done by simply adding a function to the template context, thanks to Python allowing its users to pass functions like any other object. In this recipe, we'll see how to write a custom context processor.

How to do it...

To write a custom context processor, follow...

Creating a custom Jinja2 filter

After looking at the previous recipe, experienced developers might wonder why we used a context processor for the purpose of creating a well-formatted product name. Well, we can also write a filter for the same purpose, which will make things much cleaner. A filter can be written to display the descriptive name of a product, as shown in the following example:

@product_blueprint.app_template_filter('full_name') 
def full_name_filter(product): 
    return '{0} / {1}'.format(product['category'], 
product['name'])

This can also be used as follows:

{{ product|full_name }} 

The preceding code will yield a similar result as in the previous recipe. Moving on, let's now take things to a higher level by using external libraries to format currency.

...

Creating a custom macro for forms

Macros allow us to write reusable pieces of HTML blocks. They are analogous to functions in regular programming languages. We can pass arguments to macros as we do to functions in Python, and we can then use them to process an HTML block. Macros can be called any number of times, and the output will vary as per the logic inside them. In this recipe, let's understand how to write a macro in Jinja2.

Getting ready

Macros in Jinja2 are a very common topic and have a lot of use cases. Here, we will just take a look at how a macro can be created and then used after importing it.

How to do it...

...

Advanced date and time formatting

Date and time formatting is a painful thing to handle in web applications. Such formatting in Python, using the datetime library, often increases overhead and is pretty complex when it comes to the correct handling of time zones. We should standardize timestamps to UTC when they are stored in the database, but this means that the same needs to be processed every time it is presented to users around the world.

Instead, it is smarter to defer this processing to the client side, that is, the browser. The browser always knows the current time zone of its user and will therefore be able to manipulate the date and time information correctly. This approach also reduces any unnecessary overhead from our application servers. In this recipe, we will understand how to achieve this. We will use Moment.js for this purpose.

In this recipe, it is assumed that...
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Key benefits

  • Explore Flask 1.0.3 and Python 3.7, along with useful insights into microservices
  • Get the most out of the powerful Flask framework and maintain the flexibility of your design choices
  • Write cleaner and maintainable code with the help of sample apps

Description

Flask, the lightweight Python web framework, is popular thanks to its powerful modular design that lets you build scalable web apps. With this recipe-based guide, you’ll explore modern solutions and best practices for Flask web development. Updated to the latest version of Flask and Python 3, this second edition of Flask Framework Cookbook moves away from some of the old and obsolete libraries and introduces new recipes on cutting-edge technologies. You’ll discover different ways of using Flask to create, deploy, and manage microservices. This Flask Python book starts by covering the different configurations that a Flask application can make use of, and then helps you work with templates and learn about the ORM and view layers. You’ll also be able to write an admin interface and get to grips with debugging and logging errors. Finally, you’ll learn a variety of deployment and post-deployment techniques for platforms such as Apache, Tornado, and Heroku. By the end of this book, you’ll have gained all the knowledge you need to confidently write Flask applications and scale them using standard industry practices.

Who is this book for?

If you are a web developer who wants to learn more about developing scalable and production-ready applications in Flask, this is the book for you. You’ll also find this book useful if you are already aware of Flask's major extensions and want to use them for better application development. Basic Python programming experience along with basic understanding of Flask is assumed.

What you will learn

  • Explore web application development in Flask, right from installation to post-deployment stages
  • Make use of advanced templating and data modeling techniques
  • Discover effective debugging, logging, and error handling techniques in Flask
  • Integrate Flask with different technologies such as Redis, Sentry, and MongoDB
  • Deploy and package Flask applications with Docker and Kubernetes
  • Design scalable microservice architecture using AWS Lambda continuous integration and continuous deployment
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Publication date, Length, Edition, Language, ISBN-13
Publication date : Jul 17, 2019
Length: 302 pages
Edition : 2nd
Language : English
ISBN-13 : 9781789951295
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Length: 302 pages
Edition : 2nd
Language : English
ISBN-13 : 9781789951295
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Table of Contents

14 Chapters
Flask Configurations Chevron down icon Chevron up icon
Templating with Jinja2 Chevron down icon Chevron up icon
Data Modeling in Flask Chevron down icon Chevron up icon
Working with Views Chevron down icon Chevron up icon
Webforms with WTForms Chevron down icon Chevron up icon
Authenticating in Flask Chevron down icon Chevron up icon
RESTful API Building Chevron down icon Chevron up icon
Admin Interface for Flask Apps Chevron down icon Chevron up icon
Internationalization and Localization Chevron down icon Chevron up icon
Debugging, Error Handling, and Testing Chevron down icon Chevron up icon
Deployment and Post-Deployment Chevron down icon Chevron up icon
Microservices and Containers Chevron down icon Chevron up icon
Other Tips and Tricks Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon

Customer reviews

Top Reviews
Rating distribution
Full star icon Full star icon Full star icon Half star icon Empty star icon 3.5
(11 Ratings)
5 star 54.5%
4 star 9.1%
3 star 0%
2 star 9.1%
1 star 27.3%
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Rajendra Sharma Sep 05, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
He had the most sagacious way to structure the book and very well laid out with wonderful examples.He teaches all the new concepts via an actual app that you can make along with him. What makes this especially amazing/helpful is the subject matter itself.
Amazon Verified review Amazon
Richard Jun 04, 2021
Full star icon Full star icon Full star icon Full star icon Full star icon 5
i've been using python flask and django [with bulma and bootstrap] for a good while now and until now i much preferred django as a web framework as it is very powerful and flask comes as a bare bones framework with very little out of the box.i've read the usual flask reference books and although they are comprehensive they can be verbose and it's not so easy to find the snippets that you need.this book is well organised, presented and cross referenced so that you can go to relevant sections in a flash.my motivation for choosing this book was to understand flask blueprints better as i was getting annoying circular imports. not only can i now organise my code but i have an excellent reference collection of extensions that i can use out of the box to make my apps much more functional.highly recommended
Amazon Verified review Amazon
debashish Feb 21, 2021
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Concise introductions to a broad range of Flask topics.
Amazon Verified review Amazon
Ashish Desai Apr 12, 2020
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Perfect book for folks who are used to pgrogramming and need a quick reference to solve a specific scenario. Covers most use cases any developer will encounter during 90% of their dev time
Amazon Verified review Amazon
Alex Sep 11, 2023
Full star icon Full star icon Full star icon Full star icon Full star icon 5
It's a great book and I used it to create several services, but I just wish I had not started with Flask but used Django instead. Yes, you can get a webserver running with five lines of code and you can build everything using Flask and SqlAlchemy and you can also build a house only using a screwdriver and enough determination.But if you want to build a serious web application and need a lot of features, just do yourself a favour, stop here and start learning Django.
Amazon Verified review Amazon
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