如何确保Python字典的键为小写？

Question

我有一个字典（dict），我想用simplejson把它转换成JSON格式。

我该怎么做才能确保字典里的所有键都是小写字母呢？

    {
        "DISTANCE": 17.059918745802999, 
        "name": "Foo Bar", 
        "Restaurant": {
            "name": "Foo Bar", 
            "full_address": {
                "country": "France", 
                "street": "Foo Bar", 
                "zip_code": "68190", 
                "city": "UNGERSHEIM"
            }, 
            "phone": "+33.389624300", 
            "longitude": "7.3064454", 
            "latitude": "47.8769091", 
            "id": "538"
        }, 
        "price": "", 
        "composition": "", 
        "profils": {}, 
        "type_menu": "", 
        "ID": ""
    },

补充说明：感谢大家关注我的问题，抱歉我没有详细解释我为什么想这样做。其实我是想修复django-piston里的JSONEmitter。

Answer 1

这是我的解决方案：

def lower_key(in_dict):
    if type(in_dict) is dict:
        out_dict = {}
        for key, item in in_dict.items():
            out_dict[key.lower()] = lower_key(item)
        return out_dict
    elif type(in_dict) is list:
        return [lower_key(obj) for obj in in_dict]
    else:
        return in_dict

Answer 2

这里有一个解决方案，它禁止使用小写字母作为键：

class LowerCaseDict(dict):
    def __setitem__(self, key, val):
        if not key.islower():
            raise TypeError, "%s key must be lowercase" % key
        dict.__setitem__(self, key, val)

ld = LowerCaseDict()
ld['g']='g'

Answer 3

>>> d = {"your": "DATA", "FROM": "above"}
>>> dict((k.lower(), v) for k, v in d.iteritems())
{'from': 'above', 'your': 'DATA'}
>>> def lower_keys(x):
...   if isinstance(x, list):
...     return [lower_keys(v) for v in x]
...   elif isinstance(x, dict):
...     return dict((k.lower(), lower_keys(v)) for k, v in x.iteritems())
...   else:
...     return x
...
>>> lower_keys({"NESTED": {"ANSWER": 42}})
{'nested': {'answer': 42}}

当然可以！请把你想要翻译的内容发给我，我会帮你用简单易懂的语言解释清楚。