Problems while serializing ValuesQuerySet object to json in django - json

Question

Im not able to serialize a ValuesQuerySet object to json data, i´ve found multiple solutions to this gap, but this case is different because i need to follow the Foreign Keys values.
from task_manager.models import UserTasks
data=UserTasks.objects.filter(user__username="root",server_id=2).values("server_id__mnemonic")
The previous query returns something like this:
>>> print data
[{'server_id__mnemonic': u'lol'}, {'server_id__mnemonic': u'lol'}, {'server_id__mnemonic': u'lol'},.......]
But when I try to serialize it to JSON format raises the next exception:
>>> json_data = serializers.serialize('json',data)
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "C:\Python27\lib\site-packages\django\core\serializers\__init__.py", line 122, in serialize
s.serialize(queryset, **options)
File "C:\Python27\lib\site-packages\django\core\serializers\base.py", line 45, in serialize
concrete_model = obj._meta.concrete_model
AttributeError: 'dict' object has no attribute '_meta'
>>> type(data)
<class 'django.db.models.query.ValuesQuerySet'>
I´ve found in the official Django manual a solution that says: If you only want a subset of fields to be serialized, you can specify a fields argument to the serializer:
from django.core import serializers
data = serializers.serialize('xml', SomeModel.objects.all(), fields=('name','size'))
But with this code, i cannot get the foreign keys values i want.
Thanks

Answer 1

values() gives you a ValuesQuerySet which you can serialize by converting it to a list and using json module, no need to involve Django serializers here:
import json
from task_manager.models import UserTasks
data = UserTasks.objects.filter(user__username="root",server_id=2).values("server_id__mnemonic")
print json.dumps(list(data))
Another option would to be use serializers.serialize() with specifying fields argument:
data = UserTasks.objects.filter(user__username="root",server_id=2)
print serializers.serialize('json', data, fields=('server_id__mnemonic', ))