The goal of this article is to help beginners to code their first app in Flask, the famous library written in Python. For newcomers,
Flask is a lightweight web application framework written in Python. Sometimes classified as a microframework, Flask provides a lightweight codebase that can be easily extended to become an API, a simple web app, or a complex eCommerce platform.
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Python can be downloaded from the official website. Choose the installer for your operating system, download, and click a few times.
python --version in a terminal window, you should see something like this:
$ python --version Python 3.7.2
We have two options here. Install Flask using a virtual environment or globally. I will choose the simple option:
$ pip install Flask $ pip freeze | grep Flask
First command install Flask, the second will print the version.
✨ Next step: decide the project structure
Flask leaves the organization of your web application up to you. The whole app can be saved in a single file or break down in multiple files or packages. The first two options are:
- Single module structure, where all files are saved in the same directory. This structure is suitable for a small project, or learning projects.
- Basic Package structure - if your project is not a small one anymore, maybe this project structure is recommended.
We can see now a much more organized directory structure where each file represents:
run.py- app launcher
requirements.txt- the file with the project required modules
app / __init__.py- the constructor for our app
✨ Add code and run the app
I will choose the package structure and create a few files to code the app. The minimal project structure requires two files:
<ROOT> / run.py / app / / app / __init__.py
The contents of
from app import app if __name__ == "__main__": app.run()
The contents of
from flask import Flask app = Flask(__name__) @app.route('/') def hello(): return 'Hello Coder, you are up!'
✨ Set up the environment
Before running your app you must set the variable FLASK_APP, to inform Flask what should be executed first
- Set up for Unix:
- Set up for Windows CMD
- Set up for Windows Powershell
$env:FLASK_APP = "run.py"
Navigate to the directory where
run.py was saved, and type
localhost:5000 in your preferred browser you should see the app running.
✨ Integrate a design
✨ The new structure of our project
Integrate a new design is quite an easy task, and the steps are:
- copy the UI kit assets under the directory
app / static / assets
- add the index.html under the
✨ Updated files, to render the template
- The app
from flask import Flask, render_template app = Flask(__name__) @app.route('/hello') def hello(): return 'Hello Coder, you are up!' @app.route('/') def index(): return render_template( 'layouts/default.html', title='Flask - Learn by Coding', description='Simple Flask tutorial for beginners.', content=render_template('pages/index.html') )
The above code does the following:
- Load the default layout
- Inject three variables in the template: page
✨ Structure of the layout page
✨ Structure of the index page
Thanks for reading!
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