Flask tutorial: All You Need to Learn to Master

The concept of web development has garnered immense popularity with the mind-boggling growth in websites and web applications. Python is widely used to build server-side web applications and perfectly syncs with frameworks that make web development easier. One such framework is Flask, a small, lightweight and flexible Python web framework that lets developers build real-world applications using a single Python file.

If you have been looking to understand the Flask basics, here is a Flask tutorial to help you get started with the handy Python web framework.

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What is Flask?

Flask is a web development framework developed by Armin Ronacher as part of the popular Python-based Pocoo projects. The framework is based on the Pocoo projects Werkzeug WSGI toolkit and the Jinja2 template engine. 

Let’s understand these terms in a bit more detail below.

WSGI, or the Web Server Gateway Interface, is a standard for Python web application development. It specifies a familiar interface between a Python-based web application and a web server.

Werkzeug is a comprehensive collection of libraries used to create WSGI-compatible web applications in Python. In other words, Werzeug provides the set of utilities for creating Python applications to interact with WSGI servers. 

Jinja2 is a templating language for Python developers made after Django’s template. You can use Jinja2 to create XML, HTML or other markup formats that return to the user through an HTTP request.

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Prerequisites to Learning Flask

To follow this Flask tutorial better, you require the following:

• A local Python 3 programming environment, Python 2.6 or higher for Flask installation.
• Understanding various Python 3 concepts such as data types, for loops, conditional statements and functions. 

Setting up the Flask Environment

Next, in this Flask tutorial, we will discuss the step-by-step setup process of the Flask environment.

1. A virtual Python environment builder, virtualenv helps create several Python environments simultaneously while avoiding compatibility concerns between different version libraries. 

Use the following command to install virtualenv:

Pip install virtualenv

Since the above command seeks administrator privileges, you have to add sudo before pip if you’re on Linux or macOS. Windows users need to log in as Administrators. Using Ubuntu, you can install virtualenv using its package manager.

Sudo apt-get install virtualenv

2. After the installation process is complete, a virtual environment is created in a folder.

Use command venv/bin/activate to activate the environment on Linux/OS X and venv\scripts\activate for Windows activation. 

3. The environment is now ready for Flask installation. 

4. Alternately, you can run the command pip install Flask directly without a virtual environment. 

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Building a REST API Using Flask

REST or Representational State Transfer is an architectural style used in web development and defines rules for creating web services. REST implies that when a client machine requests to get information from a server, the server machine transfers the resource’s current state back to the client machine. Simple and flexible, REST is preferable over the Simple Object Access Protocol (SOAP) due to the former’s less bandwidth usage.

Source

The methods associated with REST APIs are:

GET– The client uses GET to select or retrieve data from the server

PUT– The client uses PUT to update existing data on the server

POST– The client uses POST to write or send data to the server

DELETE– The client uses the DELETE method to delete existing data on the server

You can use the Flask framework to build a REST API in Python. Being a microframework, Flask lacks the advanced functionalities of a full-fledged framework, making it simple to build a REST API using Flask. 

You can use either of the following two ways to build a REST API in Flask:

• Using the flask_restful library.

Flask Restful is a Flask extension that supports building REST APIs in Python by using Flask as the backend. A Flask API tutorial will help you understand the concept in greater detail.

You can use the sudo pip3 install flask-restful command to install the flask_restful library.

• Using only Flask without any external libraries

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Reasons Why Flask is a Good Web Framework

Flask is an excellent framework for web application development. This section of the Flask tutorial will explain why Flask is so popular among web app frameworks.

Ease of use and flexibility

Flask lets developers customise code per the requirements, adding a layer of flexibility to the web development process. Moreover, Flask is simple to use and understand, even for beginners. 

Scalability

Flask is a highly scalable framework that fits any web app idea. So, even if you start small, Flask can handle more requests as you progressively scale. In addition, Flask modularises the codebase as it grows over time, therefore known for its scalability.

Shallow learning curve

Flask beats all other Python frameworks with its shallow learning curve, making it widely popular in the developer community. Anyone with a sound understanding of Python can easily learn Flask within a few weeks.

Support for testing

Most web application frameworks do not have the testing option, a crucial phase of the software development lifecycle. However, Flask comes with an in-built unit testing feature that lets developers test their apps before going live. Additional features of Flask, such as an in-built development server, restful request dispatching and a fast debugger, make the framework a standard choice.

Better control over codes

Flask has a small codebase, and developers have complete control over it. The framework lets developers choose the components they want for a particular application and provides sufficient control over its various extensions. 

Allows experimentation

Most importantly, Flask gives developers the freedom to adapt to and experiment with emerging technologies and use agile development methodologies at their finest. Moreover, Flask helps developers improve and modify their products, backed by quick integration and support systems. 

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