在python中使用lambda或helper方法避免for循环重复

Question

我有下面这个简单的类，我想知道是否有一个简单的方法来使用lambda，decorator，或helper method，等等。。。要避免在CODENAMES和ALL_DEFAULTS的每个方法中出现重复的for循环？你知道吗

class classproperty(object):
    """
    When used to decorate a method in a class, that method will behave
    like as a class property.
    """
    def __init__(self, f):
        # f - the func that's being decorated
        self.f = f

    def __get__(self, obj, cls):
        # call the func on the class
        return self.f(cls)

class PermissionInfo(object):

    MODELS = ['ticket', 'person', 'role']
    PERMS = ['view', 'add', 'change', 'delete']

    @classproperty
    def CODENAMES(cls):
        codenames = []
        for p in cls.PERMS:
            for m in cls.MODELS:
                codenames.append('{}_{}'.format(p, m))
        return codenames

    @classproperty
    def ALL_DEFAULTS(cls):
        ret = {}

        for p in cls.PERMS:
            for m in cls.MODELS:
                ret["{}_{}".format(p, m)] = False

        return ret

重复for循环是每个方法的此部分：

# ...
for p in cls.PERMS:
    for m in cls.MODELS:
#...

Answer 1

你也许可以用这样的方法：

MODEL_PERMS = list(map(lambda t: "{}_{}".format(t[0],t[1]), itertools.product(MODELS, PERMS)))