A more pythonic way to define an enum with dynamic members

Question

I needed to create an enum to represent the ISO country codes. The country code data comes from a json file which can be obtained from: https://github.com/lukes/ISO-3166-Cou

Answer 1

Yes, there is a way to define the enum using the alternate declaration syntax you want. It works by hiding the "ugly" code in a metaclass derived from enum.EnumMeta. If you wished, it would also be possible to define the choices() class method there, too.

import enum
import json

class CountryCodeMeta(enum.EnumMeta):
    def __new__(metacls, cls, bases, classdict):
        data = classdict['data']
        names = [(country['alpha-2'], int(country['country-code'])) for country in data]

        temp = type(classdict)()
        for name, value in names:
            temp[name] = value

        excluded = set(temp) | set(('data',))
        temp.update(item for item in classdict.items() if item[0] not in excluded)

        return super(CountryCodeMeta, metacls).__new__(metacls, cls, bases, temp)

class CountryCode(enum.Enum, metaclass=CountryCodeMeta):
    data = json.load(open('slim-2.json'))

    @classmethod
    def choices(cls):
        return ((member.value, name) for name, member in cls.__members__.items())