如何使用json.dumps()获取字典中的排序列表 [英] How to get sorted list inside a dictionary with json.dumps()

问题描述

我有以下问题:拥有如下所示的python字典:

I have the following problem: having a python dictionary like the following:

{"qqq": [{"bbb": "111"}, {"aaa": "333"}], "zzz": {"bbb": [5, 2, 1, 9]}}

我想获得一个有序的json对象，例如:

I would like to obtain an ordered json object such as:

'{"qqq": [{"aaa": "333"}, {"bbb": "111"}], "zzz": {"bbb": [1, 2, 5, 9]}}'

此刻我使用以下内容:

class ListEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, list):
            return sorted(o)
        return json.JSONEncoder.default(self, o)

print json.dumps(c, sort_keys=True, cls=ListEncoder)

但是对象内部的两个列表未排序，我得到:

But the two list inside my object are not sorted, and I get:

'{"qqq": [{"bbb": "111"}, {"aaa": "333"}], "zzz": {"bbb": [5, 2, 1, 9]}}'

可能是因为自定义JSONEncoder跳过了一种已经知道如何管理(列表)的类型.

probably because the custom JSONEncoder skips a type that already knows how to manage (list).

下面的Martijn解决方案非常适合上面的示例，但是不幸的是，我必须管理更复杂，更深入的词典:例如以下两个

Martijn solution below works perfectly for the example above, but unfortunately I have to manage more complicated dictionaries, with a bigger depth: for example the following two

a = {
    'aaa': 'aaa',
    'op': 'ccc',
    'oppa': {
        'ggg': [{'fff': 'ev'}],
        'flt': {
            'nnn': [
                {
                'mmm': [{'a_b_d': [6]},{'a_b_c': [6,7]}]
                },
                {
                    'iii': [3, 2, 4, 5]
                }
            ]
        }
    },
    'rrr': {},
    'ttt': ['aaa-bbb-ccc']
}
b = {
    'aaa': 'aaa',
    'op': 'ccc',
    'oppa': {
        'ggg': [{'fff': 'ev'}],
        'flt': {
            'nnn': [
                {
                    'iii': [2, 3, 4, 5]
                },
                {
                'mmm': [{'a_b_c': [6,7]},{'a_b_d': [6]}]
                }
            ]
        }
    },
    'rrr': {},
    'ttt': ['aaa-bbb-ccc']
}

如果对同一列表中的列表进行排序，它们将是相同的. 但是它们不在上面的类中，我得到了2个不同的json字符串:

They would be the same if the lists inside the same would be sorted. But they aren't with the class above, and I get 2 different json strings:

{"aaa": "aaa", "op": "ccc", "oppa": {"flt": {"nnn": [{"iii": [3, 2, 4, 1]}, {"mmm": [{"a_b_d": [6]}, {"a_b_c": [6, 7]}]}]}, "ggg": [{"fff": "ev"}]}, "rrr": {}, "ttt": ["aaa-bbb-ccc"]}
{"aaa": "aaa", "op": "ccc", "oppa": {"flt": {"nnn": [{"iii": [2, 3, 4, 5]}, {"mmm": [{"a_b_c": [6, 7]}, {"a_b_d": [6]}]}]}, "ggg": [{"fff": "ev"}]}, "rrr": {}, "ttt": ["aaa-bbb-ccc"]}

有解决此问题的主意吗?

Any idea to fix this?

推荐答案

default不用于列表.该方法仅适用于编码器不知道如何处理的类型.改写encode方法:

default isn't called for lists; that method is only for types the encoder doesn't know how to handle. Override the encode method instead:

class SortedListEncoder(json.JSONEncoder):
    def encode(self, obj):
        def sort_lists(item):
            if isinstance(item, list):
                return sorted(sort_lists(i) for i in item)
            elif isinstance(item, dict):
                return {k: sort_lists(v) for k, v in item.items()}
            else:
                return item
        return super(SortedListEncoder, self).encode(sort_lists(obj))

这实际上只是在编码之前对所有列表进行排序(递归)；可以在将其传递给json.dumps()之前完成此操作，但这是编码器职责的一部分，就像对键进行排序一样.

This essentially just sorts all lists (recursively) before encoding; this could have been done before passing it to json.dumps() but this way it is part of the responsibility of the encoder, just like sorting the keys is.

演示:

>>> json.dumps(c, sort_keys=True, cls=SortedListEncoder)
'{"qqq": [{"aaa": "333"}, {"bbb": "111"}], "zzz": {"bbb": [1, 2, 5, 9]}}'
>>> json.dumps(a, sort_keys=True, cls=SortedListEncoder)
'{"aaa": "aaa", "op": "ccc", "oppa": {"flt": {"nnn": [{"iii": [2, 3, 4, 5]}, {"mmm": [{"a_b_c": [6, 7]}, {"a_b_d": [6]}]}]}, "ggg": [{"fff": "ev"}]}, "rrr": {}, "ttt": ["aaa-bbb-ccc"]}'
>>> json.dumps(b, sort_keys=True, cls=SortedListEncoder)
'{"aaa": "aaa", "op": "ccc", "oppa": {"flt": {"nnn": [{"iii": [2, 3, 4, 5]}, {"mmm": [{"a_b_c": [6, 7]}, {"a_b_d": [6]}]}]}, "ggg": [{"fff": "ev"}]}, "rrr": {}, "ttt": ["aaa-bbb-ccc"]}'

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