import os

if not os.getenv('SECRET_KEY'):
    os.environ['SECRET_KEY'] = str(os.urandom(24))


class Config(object):
    """Parent configuration class."""
    DEBUG = False
    CSRF_ENABLED = True
    SECRET_KEY = os.getenv('SECRET_KEY')
    SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL')


class DevelopmentConfig(Config):
    """Configurations for Development."""
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/flask_db'


class TestingConfig(Config):
    """Configurations for Testing, with a separate test database."""
    TESTING = True
    SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/test_db'
    DEBUG = True


class StagingConfig(Config):
    """Configurations for Staging."""
    DEBUG = True


class ProductionConfig(Config):
    """Configurations for Production."""
    DEBUG = False
    TESTING = False


app_config = {
    'development': DevelopmentConfig,
    'testing': TestingConfig,
    'staging': StagingConfig,
    'production': ProductionConfig,
}

import os


class Config(object):
    """Parent configuration class."""
    DEBUG = False
    CSRF_ENABLED = True
    SECRET_KEY = os.getenv('SECRET_KEY')
    SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL')


class DevelopmentConfig(Config):
    """Configurations for Development."""
    DEBUG = True
    SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/flask_db'


class TestingConfig(Config):
    """Configurations for Testing, with a separate test database."""
    TESTING = True
    SQLALCHEMY_DATABASE_URI = 'postgresql://localhost/test_db'
    DEBUG = True


class StagingConfig(Config):
    """Configurations for Staging."""
    DEBUG = True


class ProductionConfig(Config):
    """Configurations for Production."""
    DEBUG = False
    TESTING = False


app_config = {
    'development': DevelopmentConfig,
    'testing': TestingConfig,
    'staging': StagingConfig,
    'production': ProductionConfig,
}

Edit secret_key configurations