JSONからPythonオブジェクトを生成する方法

json – JavaScript Object Notation シリアライザ - Python Module of the Week
の写経である

なんとなくの説明は　JSONからPerlオブジェクトを生成する方法 - Qiita　を参照のこと

class MyObj(object):
    def __init__(self, s, y):
        self.s = s
        self.y = y

    def __repr__(self):
        return '<MyObj(%s)>' % self.s


def main():
    import json

    obj = MyObj('instance value goes here', "a")
    print(obj)

    # print('First attempt')
    try:
        print(json.dumps(obj))
    except TypeError, err:
        print("ERROR:", err)

    def convert_to_builtin_type(obj):
        # print('default(', repr(obj), ')')
        # Convert objects to a dictionary of their representation
        d = {'__class__': obj.__class__.__name__,
             '__module__': obj.__module__,
             }
        d.update(obj.__dict__)
        return d

    def dict_to_object(d):
        if '__class__' in d:
            class_name = d.pop('__class__')
            module_name = d.pop('__module__')
            module = __import__(module_name)
            # print('MODULE:', module)
            class_ = getattr(module, class_name)
            # print('CLASS:', class_)
            args = dict((key.encode('ascii'), value) for key, value in d.items())
            # print('INSTANCE ARGS:', args)
            inst = class_(**args)
        else:
            inst = d
        return inst

    # print('With default')

    json_txt = json.dumps(obj, default=convert_to_builtin_type)
    print(json_txt)

    obj2 = json.loads(json_txt, object_hook=dict_to_object)
    print(obj2)
    print(obj2.s)


if __name__ == '__main__':
    main()
    exit(0)

"""
<MyObj(instance value goes here)>
ERROR: <MyObj(instance value goes here)> is not JSON serializable
{"y": "a", "s": "instance value goes here", "__module__": "__main__", "__class__": "MyObj"}
<MyObj(instance value goes here)>
instance value goes here
"""