$ export FLASK_APP=hello.py
$ python -m flask run
* Running on http://127.0.0.1:5000/
# I am assuming that you have configured the app name as "app"
if __name__ == "__main__":
app.run()
app = Flask(__name__)
if __name__ == "__main__":
app.run()
FLASK_DEBUG=1 FLASK_ENV=development flask run
from flask import Flask
app = Flask(__name__)