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Asked: 2024-11-27T07:47:09+00:00

Flask App Tutorial

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Hello Coders,

This article might help beginners to code a simple App using Flask, the popular Python Framework. If something relevant for a beginner is not here or you are a beginner and a section is not presented well enough, don't hesitate to ask anything in the comments section. Being almost daily on Dev, there are big chances to respond.

Thank you! Content provided by AppSeed – App Generator.

Topics

  • Flask Introduction
  • Set up (aka environment)
  • Edit the code
  • Start the application
  • Summary

Flask Introduction

👉 Flask is a lightweight web application framework. It is designed to make getting started quick and easy, with the ability to scale up to complex applications. Compared to Django, Flask provides a lightweight codebase and more freedom to the developer.

Flask is written in Python and it does not require particular tools or libraries.

  • Flask – the official website
  • Flask Docs – learn what Flask has to offer in detail

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Set up

👉 To code a Flask application we need some tools properly set up in our workstation. Here is the recommended list:

To finish this tutorial we will work with the console (aka terminal). In Windows, we can use Powershell or the corespondent xterm for Linux. The next step is to open a terminal and check the Python installation: 

$ python --version Python 3.8.4
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If the above command returns an error please double-check the Python installation and get back here after to follow up the next steps.

Install Flask

Flask is basically a Python package and we can install it with ease via a tool shipped by Python: PIP. 

$ $ pip install Flask
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Edit the code

👉 Create a new file named hello.py in the current directory and add this code:

from flask import Flask  app = Flask(__name__)  @app.route('/') def hello():     return f'My first Flask APP!'
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This simple code snippet ( also saved here ) does the following:

  • Import Flask, the library that we've installed in the previous step
  • app object is constructed by Flask. At this point, we can use all features provided by Flask
  • define a default route that will return a simple Hello message when someone accesses our application using the browser

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Start the application

👉 Flask being such a nice framework, comes with a simple server to help us check the code without being forced to install 3rd party tools. To use it and see our minimal app running in the browser, a variable must be exported in the environment that informs Flask the name of the file: 

$ export FLASK_APP=run.py
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Once we have this variable we can call Flask: 

$ flask run
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By default Flask will start the application on address 'localhost:5000'. If we visit the application in the browser, we should see the message:

My first Flask APP!

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Summary

👉 During this tutorial, we've learned a few basic things:

  • What is Flask and how to install it
  • We've coded a super simple app
  • We've seen the application running in the browser

Where to go from here?

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Btw, my (nick) name is Sm0ke and I'm pretty active also on Twitter.

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