example.py

DEFAULTS = {
    'title': None,
    'output': 'build',
    'strict': False,
}

VALIDATORS = {
    'title': must_be(str, required=True),
    'output': path_validator(exists=True, directory=True, file=False)
    'title': must_be(bool, required=True),
}

config = DEFAULTS.copy()
config.update(user_config) # loaded from a file

for option_name, value in config.items():

    try:
        VALIDATORS[option_name](value)
    except ValidationError as e:
        print(e)