How to get an ordered list of keys from a json file?

[HLammers]

Let’s say I have a json file with the following structure:

{
"list of objects": {
"key 1": {...},
"key 2": {...},
"key 3": {...},
...
},
...
}

What I need is a list of the keys in ‘list of objects’, in exactly the same order as in the json file.

If I load it this way, I get a randomly ordered list:

import ujson as json
json_file = open('json_file.json')
data = json.load(json_file)
list_of_keys = list(data['list of objects'])

Is there any way to get a list of keys in the original order? I’ve tried using object_pairs_hook=OrderedDict, but the MicroPython implementation of json/ujson doesn’t seem to implement object_pairs_hook.

[andrewleech]

I proposed this by default in #6135

[HLammers]

Thanks @andrewleech , really appreciating your endevours to resolve this!
Since you’ve proposed this about 4 years ago, I’d expect it will take a long time before we see anything like that in the production version of MicroPython. Any idea for a workaround in the meanwhile? Or do I need to rebuild by json file to include an array with ordered keys (assuming arrays are imported as ordered lists - I didn’t test it), plus all the hassle to keep both aligned?

[andrewleech]

I couldn't come up with a workaround myself, hence the PR. I included it in builds for the project that needed json ordering.

Lists are definitely imported in order, so that's possible, but yeah certainly uglier.