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Code a simple app In Flask

How To code a simple Flask Application

This page explains how to code a simple Flask application.

✅ Prerequisites​

  • Basic programming knowledge in Python
  • Basic Flask knowledge
  • Comfortable using a terminal

✅ A minimal app​

Before using Flask, we need to install it. Open a terminal and type:

$ pip install Flask

Create a new file hello.py with the following content:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return f'Hello from Flask!'

Once the file is saved, let's start the app:

$ # Set up the DEBUG environment
$ # (Unix/Mac) export FLASK_ENV=development
$ # (Windows) set FLASK_ENV=development
$ # (Powershell) $env:FLASK_ENV = "development"
$
$ flask run
$ # Visit the app in browser: http://127.0.0.1:5000/

By visiting the app in the browser we should see "Hello from Flask" message.

✅ Resources​