regions.py

from django.core.exceptions import ImproperlyConfigured, ValidationError
from django.forms.fields import Select
from django.utils import importlib


def load_path_attr(path):
    i = path.rfind(".")
    module, attr = path[:i], path[i+1:]
    try:
        mod = importlib.import_module(module)
    except ImportError as e:
        raise ImproperlyConfigured("Error importing {0}: '{1}'".format(module, e))
    try:
        attr = getattr(mod, attr)
    except AttributeError:
        raise ImproperlyConfigured("Module '{0}' does not define a '{1}'".format(module, attr))
    return attr


SUPPORTED_COUNTRIES = {
    "US": {
        "field": "localflavor.us.forms.USStateField",
        "choices": "localflavor.us.us_states.STATE_CHOICES",
        "label": "State"
    }
}


class LocalFlavorPicker(object):

    def __init__(self, country_code):
        self.code = country_code
        self.region_field = None
        self.config = SUPPORTED_COUNTRIES.get(self.code.upper())
        if self.config:
            Field = load_path_attr(self.config["field"])
            choices = [("", "---------")] + list(self.choices)
            self.region_field = Field(
                widget=Select(choices=choices),
                required=False,
                label=self.config["label"]
            )

    @property
    def choices(self):
        if self.config:
            return load_path_attr(self.config["choices"])
        return []

    def assert_valid_region(self, region_code):
        if self.choices and region_code not in self.choices:
            raise ValidationError("{0} is an invalid region for {1}".format(
                region_code,
                self.code
            ))