instance configuration in Flask

config.py

## instance/config.py

HELLO_ENABLED = False

main.py

from flask import Flask
import os

class Config:
    """basic configuration parameters passed to the Flask app"""

    # basic config
    SECRET_KEY = 'changeme'
    WTF_CSRF_SECRET_KEY = 'changemetoo'
    DEBUG=True
    
    # application feature flags
    HELLO_ENABLED = True


app = Flask(__name__, instance_relative_config=True)

app.config.from_object(Config)

# override default settings with those present in /instance/config.py
# this will raise an exception if file is not present
app.config.from_pyfile('config.py')

@app.route('/')
def hello_world():
    if app.config['HELLO_ENABLED']:
        return 'helloworld'