config.py

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

class Config:
    SECRET_KEY = os.environ.get('SECRET_KEY')
    SQLALCHEMY_TRACK_MODIFICATIONS = False
    
    @staticmethod
    def init_app(app):
        pass

class Testing(Config):
    TESTING = True
    SQLALCHEMY_DATABASE_URI = os.environ.get('TEST_DATABASE_URL') or \
            'sqlite://'

class DevelopmentConfig(Config):
    DEBUG=True
    SQLALCHEMY_DATABASE_URI = os.environ.get('TEST_DATABASE_URL') or \
            'sqlite:///' + os.path.join(basedir, 'data-dev.sqlite')    

class ProductionConfig(Config):
    SQLALCHEMY_DATABASE_URI = os.environ.get('DATABASE_URL') or \
            'sqlite:///' + os.path.join(basedir, 'data.sqlite')

config = {
    'testing': Testing,
    'development': DevelopmentConfig,
    'production':ProductionConfig,
    'default': DevelopmentConfig
        }