首先，查看不进行子类化时所需的代码EnumMeta：

stdlib方式

from enum import Enum
import json

class BaseCountry(Enum):
    def __new__(cls, record):
        member = object.__new__(cls)
        member.country_name = record['name']
        member.code = int(record['country-code'])
        member.abbr = record['alpha-2']
        member._value_ = member.abbr, member.code, member.country_name
        if not hasattr(cls, '_choices'):
            cls._choices = {}
        cls._choices[member.code] = member.country_name
        cls._choices[member.abbr] = member.country_name
        return member                
    def __str__(self):
        return self.country_name

Country = BaseCountry(
        'Country',
        [(rec['alpha-2'], rec) for rec in json.load(open('slim-2.json'))],
        )

该aenum方法 1 2

from aenum import Enum, MultiValue
import json

class Country(Enum, init='abbr code country_name', settings=MultiValue):
    _ignore_ = 'country this'  # do not add these names as members
    # create members
    this = vars()
    for country in json.load(open('slim-2.json')):
        this[country['alpha-2']] = (
                country['alpha-2'],
                int(country['country-code']),
                country['name'],
                )
    # have str() print just the country name
    def __str__(self):
        return self.country_name

上面的代码适合一次性枚举-但是如果从JSON文件创建枚举对您来说很普遍怎么办？想象一下您是否可以这样做：

class Country(JSONEnum):
    _init_ = 'abbr code country_name'  # remove if not using aenum
    _file = 'some_file.json'
    _name = 'alpha-2'
    _value = {
            1: ('alpha-2', None),
            2: ('country-code', lambda c: int(c)),
            3: ('name', None),
            }

如你看到的：

• _file 是要使用的json文件的名称
• _name 是该名称应使用的路径
• _value是将路径映射到值3的字典
• _init_指定不同值组件的属性名称（如果使用aenum）

JSON数据摘自https://github.com/lukes/ISO-3166-Countries-with-Regional-Codes-
以下是简短摘录：

[{“ name”：“ Afghanistan”，“ alpha-2”：“ AF”，“国家/地区代码”：“ 004”}，

{“ name”：“ÅlandIslands”，“ alpha-2”：“ AX”，“国家/地区代码”：“ 248”}，

{“名称”：“阿尔巴尼亚”，“ alpha-2”：“ AL”，“国家代码”：“ 008”}，

{“名称”：“阿尔及利亚”，“ alpha-2”：“ DZ”，“国家/地区代码”：“ 012”}]

这是JSONEnumMeta课程：

class JSONEnumMeta(EnumMeta):

    @classmethod
    def __prepare__(metacls, cls, bases, **kwds):
        # return a standard dictionary for the initial processing
        return {}

    def __init__(cls, *args , **kwds):
        super(JSONEnumMeta, cls).__init__(*args)

    def __new__(metacls, cls, bases, clsdict, **kwds):
        import json
        members = []
        missing = [
               name
               for name in ('_file', '_name', '_value')
               if name not in clsdict
               ]
        if len(missing) in (1, 2):
            # all three must be present or absent
            raise TypeError('missing required settings: %r' % (missing, ))
        if not missing:
            # process
            name_spec = clsdict.pop('_name')
            if not isinstance(name_spec, (tuple, list)):
                name_spec = (name_spec, )
            value_spec = clsdict.pop('_value')
            file = clsdict.pop('_file')
            with open(file) as f:
                json_data = json.load(f)
            for data in json_data:
                values = []
                name = data[name_spec[0]]
                for piece in name_spec[1:]:
                    name = name[piece]
                for order, (value_path, func) in sorted(value_spec.items()):
                    if not isinstance(value_path, (list, tuple)):
                        value_path = (value_path, )
                    value = data[value_path[0]]
                    for piece in value_path[1:]:
                        value = value[piece]
                    if func is not None:
                        value = func(value)
                    values.append(value)
                values = tuple(values)
                members.append(
                    (name, values)
                    )
        # get the real EnumDict
        enum_dict = super(JSONEnumMeta, metacls).__prepare__(cls, bases, **kwds)
        # transfer the original dict content, _items first
        items = list(clsdict.items())
        items.sort(key=lambda p: (0 if p[0][0] == '_' else 1, p))
        for name, value in items:
            enum_dict[name] = value
        # add the members
        for name, value in members:
            enum_dict[name] = value
        return super(JSONEnumMeta, metacls).__new__(metacls, cls, bases, enum_dict, **kwds)

# for use with both Python 2/3
JSONEnum = JSONEnumMeta('JsonEnum', (Enum, ), {})

一些注意事项：

• JSONEnumMeta.__prepare__ 返回正常 dict

• EnumMeta.__prepare__用于获取的实例_EnumDict-这是获取实例的正确方法

• 带下划线的键将被传递给实数_EnumDict优先，因为在处理枚举成员时可能需要它们

• 枚举成员的顺序与文件中的顺序相同

1披露：我是Python
stdlibEnum，enum34backport和Advanced
Enumeration（aenum） 库的作者。

2这需要aenum 2.0.5+。

3键是数字键，可以在需要多个值时按顺序保留多个值Enum。