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.
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- Flask Introduction
- Set up (aka environment)
- Edit the code
- Start the application
👉 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.
👉 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
If the above command returns an error please double-check the Python installation and get back here after to follow up the next steps.
Flask is basically a Python package and we can install it with ease via a tool shipped by Python: PIP.
$ $ pip install Flask
👉 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!'
This simple code snippet ( also saved here ) does the following:
Flask, the library that we've installed in the previous step
appobject is constructed by
Flask. At this point, we can use all features provided by Flask
- define a default
routethat will return a simple Hello message when someone accesses our application using the browser
👉 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
Once we have this variable we can call
$ flask run
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!
👉 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?
Btw, my (nick) name is Sm0ke and I'm pretty active also on Twitter.