app_config.py

import os

basedir = os.path.abspath(os.path.dirname(__file__))

class Config:
    DEBUG = False
    TESTING = False
    CSRF_ENABLED = True
    SECRET_KEY = "some key"
    SQLALCHEMY_DATABASE_URI = os.environ["DATABASE_URL"]

class ProductionConfig(Config):
    DEBUG = False

class StagingConfig(Config):
    DEVELOPMENT = True
    DEBUG = True

class DevelopmentConfig(Config):
    DEVELOPMENT = True
    DEBUG = True

class TestingConfig(Config):
    TESTING = True