Is there a way to run flask in debug mode using the `flask run` command without setting environment variables?

Question

I'm trying to run a flask application in debug mode (or at least a mode where it will reload after changing the files).

I'm aware of export FLASK_ENV=development, however I am working on a university online development environment, and I lose the environment variables every time the site reloads, which while not the end of the world, is slightly annoying, and I'd rather avoid having to keep typing it (lazy I know).

If I include the following, and run using python3 main.py, debug mode is activated, however when using flask run, debug remains off.

if __name__ == "__main__":
  app.run(debug=True)

However, as I understand it, using the flask run command is the preferred way to launch the app, not using python app.py.

I've found ideas such as including the following, however none of these have activated debug mode, so I'm wondering whether it is even possible:

app.config['ENV'] = 'development'
app.config['DEBUG'] = True
app.config['TESTING'] = True

I've simplified my code to the following to see if it was an error in my original piece, but it doesn't seem to be:

from flask import Flask

app = Flask(__name__)
app.config['ENV'] = 'development'
app.config['DEBUG'] = True
app.config['TESTING'] = True

@app.route('/')
def home():
    return '<h1>debugging!</h1>'

if __name__ == "__main__":
    app.run(debug=True)

have a look at this thread: https://stackoverflow.com/a/64623193/12368419 — cizario, Oct 16 '21 at 17:38
That's excellent. I did have a look through stack exchange but couldn't find much of use. Using that `.flaskenv` file works a dream — askman, Oct 16 '21 at 18:35

score 1 · Accepted Answer · answered Oct 16 '21 at 20:12

In short, there does not seem to be a way of using flask run how I want without assigning environment variables, however using a .flaskenv file will allow environment variables to be loaded at run time.

The .flaskenv file for example could include the following ENVs among others to be loaded:

FLASK_APP=main:app
FLASK_ENV=development
FLASK_DEBUG=1

Note - this does require python-dotenv to be installed to use.

All credit to @cizario who answered here with some more detail:

https://stackoverflow.com/a/64623193/12368419

score 1 · Answer 2 · answered Oct 08 '22 at 04:30

Well, when it's Flask 2.2 or later, you can just do

flask --debug run

 * Debug mode: on
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit
 * Restarting with stat
 * Debugger is active!
 * Debugger PIN: 560-342-853

Is there a way to run flask in debug mode using the `flask run` command without setting environment variables?

2 Answers2