Replace None values with empty string in a list

I have a list of dictionary of dictionary as shown below:

[{'value': {'id': None, 'check': 'True', 'plant': '124', 'vehicle': 'Yamaha', 'productionNumber': '09467','date': [2013, 8, 09]},'id':None}]

I need to replace the None value with empty string, how to achieve this?