json_numpy.py

import numpy
import json


class EncodeFromNumpy(json.JSONEncoder):
    """
    - Serializes python/Numpy objects via customizing json encoder.
    - **Usage**
        - `json.dumps(python_dict, cls=EncodeFromNumpy)` to get json string.
        - `json.dump(*args, cls=EncodeFromNumpy)` to create a file.json.
    """
    def default(self, obj):
        import numpy
        if isinstance(obj, numpy.ndarray):
            return {
                "_kind_": "ndarray",
                "_value_": obj.tolist()
            }
        if isinstance(obj, numpy.integer):
            return int(obj)
        elif isinstance(obj, numpy.floating):
            return float(obj)
        elif isinstance(obj, range):
            value = list(obj)
            return {
                "_kind_": "range",
                "_value_": [value[0], value[-1] + 1]
            }
        return super(EncodeFromNumpy, self).default(obj)


class DecodeToNumpy(json.JSONDecoder):
    """
    - Deserializes JSON object to Python/Numpy's objects.
    - **Usage**
        - `json.loads(json_string,cls=DecodeToNumpy)` from string, use `json.load()` for file.
    """
    def __init__(self, *args, **kwargs):
        json.JSONDecoder.__init__(self, object_hook=self.object_hook, *args, **kwargs)

    def object_hook(self, obj):
        if '_kind_' not in obj:
            return obj
        kind = obj['_kind_']
        if kind == 'ndarray':
            return numpy.array(obj['_value_'])
        elif kind == 'range':
            value = obj['_value_']
            return range(value[0], value[-1])
        return obj