Question

Source

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'),
)

Question

How can I add an __iter__ method to Abilities so that I can iterate over choices?

Why?

This way I can use things like

hero.abilities = Abilities.FLY | Abilities.FIREBALL

if hero.abilities & Abilities.FIREBALL:

for k, v in Abilities:
    print k, v

in my code without having to use any magic numbers or strings, and I can also save the set of flags to the DB as a single int, or display the list in a readable format.

Other improvements are welcome.

Answer 1

There’s no need to use a dynamic type here; I’d restructure this as a simple class, for example:

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