You can create a custom encoder that returns a list
when it encounters a set
. Here’s an example:
>>> import json
>>> class SetEncoder(json.JSONEncoder):
... def default(self, obj):
... if isinstance(obj, set):
... return list(obj)
... return json.JSONEncoder.default(self, obj)
...
>>> json.dumps(set([1,2,3,4,5]), cls=SetEncoder)
'[1, 2, 3, 4, 5]'
You can detect other types this way too. If you need to retain that the list was actually a set, you could use a custom encoding. Something like return {'type':'set', 'list':list(obj)}
might work.
To illustrated nested types, consider serializing this:
>>> class Something(object):
... pass
>>> json.dumps(set([1,2,3,4,5,Something()]), cls=SetEncoder)
This raises the following error:
TypeError: <__main__.Something object at 0x1691c50> is not JSON serializable
This indicates that the encoder will take the list
result returned and recursively call the serializer on its children. To add a custom serializer for multiple types, you can do this:
>>> class SetEncoder(json.JSONEncoder):
... def default(self, obj):
... if isinstance(obj, set):
... return list(obj)
... if isinstance(obj, Something):
... return 'CustomSomethingRepresentation'
... return json.JSONEncoder.default(self, obj)
...
>>> json.dumps(set([1,2,3,4,5,Something()]), cls=SetEncoder)
'[1, 2, 3, 4, 5, "CustomSomethingRepresentation"]'