SQLAlchemy json serializer

from sqlalchemy.ext.declarative import DeclarativeMeta

class AlchemyEncoder(json.JSONEncoder):

	def default(self, obj):

		print obj.__public__
		if isinstance(obj.__class__, DeclarativeMeta):
			fields = {}
			for field in [x for x in obj.__public__) if not x.startswith('_') and x != 'metadata']:
				data = obj.__getattribute__(field)
				try:
					json.dumps(data)
					fields[field] = data

				except TypeError:
					#If the data could not be encoded, check what its instance is and assign value likewise.
					if(isinstance(data,datetime.datetime)):
						fields[field] = data.isoformat()
				# a json-encodable dict
			return fields

		return json.JSONEncoder.default(self, obj)