run the flask application code example

Example 1: flask how to run app

$ export FLASK_APP=hello.py
$ python -m flask run
 * Running on http://127.0.0.1:5000/

Example 2: run flask app from command line

# For bash do this:
set FLASK_APP=<app_name>

# For powershell do this:
$env FLASK_APP=<app_name>

# Run it like this
flask run