Flask Configuration

Cho Zin Thet
2 min readSep 21, 2021


We run basic flask app in How to create a website with Python Flask and we set ENV config value (environment) to development. In flask, we can set different values (setting) base on environment (ENV). Default ENV is production. Later we will need to set debug mode, secret key , database url and add other new values to flask. Then we deploy to server, we need to set ENV to production and change the values again. So we need to prepare to change the values base on application environment.

Print all config values in your flask app

from flask import Flaskapp = Flask(__name__)
def home():
return "This is Home Page"
if __name__ == "__main__":

Add new config value

ap.config['SECRET'] = "secret"

ENV config


ENV config value is which environment you app is running. Default ENV is production. Run production server when deploy

app.config['ENV'] = 'production'


development mode reload the code when it is changed.

When you run flask you will see above warning. Then set below code

app.config['ENV'] = 'development'

Set configuration values depend on application environment

  • create config.py
class Config(object):
DEBUG = False
class ProductionConfig(Config):
ENV = 'production'
class DevelopmentConfig(Config):
ENV = 'development'
DEBUG = True

means that in production server ENV is production. In development server ENV is development and debug mode is true.

You can set more config values.

  • in main.py
from flask import Flaskapp = Flask(__name__)
def home():
return "home"
if __name__ == "__main__":