config.py

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

class Config:
    SECRET_KEY = os.getenv('SECRET_KEY') or 'hard to guess string'
    SQLALCHEMY_COMMIT_ON_TEARDOWN = True

    @staticmethod
    def init_app(app):
        pass


class DevelopmentConfig(Config):
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = os.getenv('DEV_DATABASE_URL') or \
    'sqlite:///' + os.path.join(basedir, 'dev-db.sqlite')

class TestingConfig(Config):
    TESTING = True
    SQLALCHEMY_DATABASE_URI = os.getenv('TEST_DATABASE_URL') or \
    'sqlite:///' + os.path.join(basedir, 'test-db.sqlite')


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


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