python - 如何将 __iter__ 添加到动态类型？

Question

来源

def flags(*opts):
    keys = [t[0] for t in opts]
    words = [t[1] for t in opts]
    nums = [2**i for i in range(len(opts))]
    attrs = dict(zip(keys,nums))
    choices = iter(zip(nums,words))
    return type('Flags', (), dict(attrs))

Abilities = flags(
    ('FLY', 'Can fly'),
    ('FIREBALL', 'Can shoot fireballs'),
    ('INVISIBLE', 'Can turn invisible'),
)

问题

如何将 __iter__ 方法添加到 Abilities 以便我可以遍历 choices？

为什么？

这样我可以使用类似的东西

hero.abilities = Abilities.FLY | Abilities.FIREBALL

if hero.abilities & Abilities.FIREBALL:

for k, v in Abilities:
    print k, v

在我的代码中无需使用任何魔数(Magic Number)或字符串，我还可以将标志集作为单个 int 保存到数据库，或以可读格式显示列表。

欢迎其他改进。

Answer 1

这里不需要使用动态类型；我将其重组为一个简单的类，例如:

class flags(object):
    def __init__(self, *opts):
        keys = [t[0] for t in opts]
        words = [t[1] for t in opts]
        nums = [2**i for i in range(len(opts))]
        self.attrs = dict(zip(keys,nums))
        self.choices = zip(nums,words)

    def __getattr__(self, a):
        return self.attrs[a]

    def __iter__(self):
        return iter(self.choices)

Abilities = flags(
    ('FLY', 'Can fly'),
    ('FIREBALL', 'Can shoot fireballs'),
    ('INVISIBLE', 'Can turn invisible'),
)

print Abilities.FLY
for k, v in Abilities:
    print k, v