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如何将iter添加到动态类型?

python

mpen · 技术社区 · 15 年前

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

如何添加 __iter__ Abilities 这样我就可以重复 choices ?

这样我就可以使用

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,不必使用任何幻数或字符串,我还可以将标志集保存为单个int,或以可读格式显示列表。

5 回复 | 直到 15 年前

Glenn Maynard 15 年前

这里不需要使用动态类型;我将它重新构造为一个简单的类,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

msw 15 年前

dict 具有 __getattr__ 为什么不从一开始:

class Flags(dict):
    def __init__(self, *args):
        dict.__init__(self, args)
    def __getattr__(self, name):
         return self[name]
...

dict.__iter__() 生成键和 dict.iteritems()

Alex Martelli 15 年前

flags 应该是:

choices = iter(zip(nums,words))
attrs['__iter__'] = lambda self: choices
return type('Flags', (), dict(attrs))()

注意,我添加了一个行设置 __iter__ , 和 () return 到类型(在类型

最后一行

return type('Flags', (), attrs)()

因为没有理由复制 attrs ,这已经是 dict (但这是无伤大雅的冗余,不是致命的错误;-)。

Andrey Vlasovskikh 15 年前

__getattr__ 通过访问动态字段而不是处理元类的方法 type .

编辑:

class Abilities(object):
    def __init__(self, abilities):
        self.abilities = abilities

    def __getattr__(self, name):
        a = [x for x in self.abilities if x[0] == name]
        if len(a) != 1:
            raise AttributeError('attribute {0} not found'.format(name))
        title, id, help = a[0]
        return id

    def __iter__(self):
        return (id, help for title, id, help in self.abilities)

SPEC = [
    ('FLY', 10, 'Can fly'),
    ('FIREBALL', 13, 'Can shoot fireballs'),
    ('INVISIBLE', 14, 'Can turn invisible'),
]

abitilies = Abilities(SPEC)

hero.abilities = abilities.FLY | abilities.FIREBALL
for k, v in abilities:
    print k, v

mpen 15 年前

根据你们的建议,我想到了这个:

来源

class enumerable(object):
    def __init__(self, func, *opts):
        keys = func(len(opts))
        self.attrs = dict(zip([t[0] for t in opts], keys))
        self.opts = zip(keys, [t[1] for t in opts])
    def __getattr__(self, a):
        return self.attrs[a] 
    def __len__(self):
        return len(self.opts)
    def __iter__(self):
        return iter(self.opts)
    def __deepcopy__(self, memo):
        return self

class enum(enumerable):
    def __init__(self, *opts):
        return super(enum, self).__init__(range, *opts)

class flags(enumerable):
    def __init__(self, *opts):
        return super(flags, self).__init__(lambda l: [1<<i for i in range(l)], *opts)

### tests:

Abilities = enum(
    ('FLY', 'Can fly'),
    ('FIREBALL', 'Can shoot fireballs'),
    ('INVISIBLE', 'Can turn invisible'),
    ('FROST_NOVA', 'Can call down an ice storm'),
    ('BLINK', 'Can teleport short distances'),
)

print 'Fireball = %d' % Abilities.FIREBALL
print 'Number of options = %d' % len(Abilities) 
for k, v in Abilities:
    print '%d: %s' % (k, v)

Fireball = 1
Number of options = 5
0: Can fly
1: Can shoot fireballs
2: Can turn invisible
3: Can call down an ice storm
4: Can teleport short distances

不管出于什么原因,我的特殊应用程序需要 __deepcopy__ self .