JSON encoder class with serializer for dates and decimal numbers: serializes json objects without error

json_encoder.py

import json
import datetime
import decimal

class MyJsonEncoder(json.JSONEncoder):
    """ JSON Encoder with serializer for dates and decimal numbers """
    def default(self, obj):
        if isinstance(obj, datetime.datetime):
            return str(obj.isoformat())
        elif isinstance(obj, datetime.time):
            return str(obj.isoformat())
        elif isinstance(obj, decimal.Decimal):
            return float(obj)
        return json.JSONEncoder.default(self, obj)


if __name__ == '__main__':
    obj = {
        'time': datetime.time(15),
        'dt': datetime.datetime.utcnow(),
        'dec': decimal.Decimal(3.5)
    }
    print json.dumps(obj, cls = MyJsonEncoder)