Helpers to serialize/de-serialize generic Python objects as JSON

generic_json.py

"""Custom JSON encoder and Decoder classes to work with general Python classes

Pass these as the `cls` argument to json.dump and json.load to enable
the serialization of most Python defined "well behaved"  objects
directly as JSON.

Ref.: http://stackoverflow.com/questions/43092113/create-a-class-that-support-json-serialization-for-use-with-celery/43093361#43093361
"""

import json

class GenericJSONEncoder(json.JSONEncoder):
    def default(self, obj):
        try:
            return super().default(obj)
        except TypeError:
            pass
        cls = type(obj)
        result = {
            '__custom__': True,
            '__module__': cls.__module__,
            '__name__': cls.__name__,
            'data': obj.__dict__ if not hasattr(cls, '__json_encode__') else obj.__json_encode__
        }
        return result


class GenericJSONDecoder(json.JSONDecoder):
    def decode(self, str):
        result = super().decode(str)
        if not isinstance(result, dict) or not result.get('__custom__', False):
            return result
        import sys
        module = result['__module__']
        if not module in sys.modules:
            __import__(module)
        cls = getattr(sys.modules[module], result['__name__'])
        if hasattr(cls, '__json_decode__'):
            return cls.__json_decode__(result['data'])
        instance = cls.__new__(cls)
        instance.__dict__.update(result['data'])
        return instance