Choices

In case we want the user to specify a value from a discrete set of possible choices we can do so in the following ways:

from hanna import Configurable, String

class Settings(Configurable):
    log_level = String(choices=('info', 'warn', 'error'))
    log_level.choices = ('info', 'warn', 'error')  # Similar.

In case a value is specified that is not part of the declared possible choices a ValueError will be raised:

# raises ValueError: "log_level" Illegal choice ('debug' not in ('info', 'warn', 'error'))
settings = Settings({'log_level': 'debug'})