Flask basic commands

If there is app.py (Flask app), we can run it simply like below.

python3 app.py

However, it is recommended to use Flask own environmental variable to run  Flask app, please see below.

export FLASK_APP=app 🠔 Flask app name, it means 'app.py' export FLASK_ENV=development 🠔 We run as developement purpose, otherwise production export PORT=9010 🠔 Port number to use, normally, 80 port is already taken by running production service flask run flask run --reload 🠔 As *.py files are updated, flask reload *.py automatically as it detect any updated .py files.

Be carefull, PORT is not default Flask environmental variable, however, please see how to use it below.

if __name__ == '__main__':     port = os.getenv('PORT', default=9050)    application.run(host='0.0.0.0', port=port)

Lastly, your Flaks app is ready to launch, we should use gunicorn.

$ gunicorn -w 4 app:application 🠔 app means app.py, and application is declared in app.py