Preserve Python tuples with JSON

Question

I'm still a little new to this, so I might not know all the conventional terms for things:

Is it possible to preserve Python tuples when encoding with JSON? Right now json.loads(json.dumps(tuple)) gives me a list back. I don't want to convert my tuples to lists, but I want to use JSON. So, are there options?

The reason why: I'm creating an app that uses multi-dimensional arrays, not always the same shape. I've got some class methods that use recursion to probe the arrays and cast the endpoints as a string or int. I recently realized that (based on how my recursion works) I can use tuples to prevent deeper recursive searching of arrays (Python rawks). This could come in handy in situations where I know I for sure I won't need to be probing any deeper into my data structures.

Answer 1

You can write a highly-specialzed encoder and a decoder hook:

import json

class MultiDimensionalArrayEncoder(json.JSONEncoder):
    def encode(self, obj):
        def hint_tuples(item):
            if isinstance(item, tuple):
                return {'__tuple__': True, 'items': item}
            if isinstance(item, list):
                return [hint_tuples(e) for e in item]
            if isinstance(item, dict):
                return {key: hint_tuples(value) for key, value in item.items()}
            else:
                return item

        return super(MultiDimensionalArrayEncoder, self).encode(hint_tuples(obj))

def hinted_tuple_hook(obj):
    if '__tuple__' in obj:
        return tuple(obj['items'])
    else:
        return obj


enc = MultiDimensionalArrayEncoder()
jsonstring =  enc.encode([1, 2, (3, 4), [5, 6, (7, 8)]])

print jsonstring

# [1, 2, {"items": [3, 4], "__tuple__": true}, [5, 6, {"items": [7, 8], "__tuple__": true}]]

print json.loads(jsonstring, object_hook=hinted_tuple_hook)

# [1, 2, (3, 4), [5, 6, (7, 8)]]