Convert multiple querysets to json in django

Question

I asked a related question earlier today

In this instance, I have 4 queryset results:

action_count = Action.objects.filter(complete=False, onhold=False).annotate(action_count=Count('name'))
hold_count = Action.objects.filter(onhold=True, hold_criteria__isnull=False).annotate(action_count=Count('name'))
visible_tags = Tag.objects.filter(visible=True).order_by('name').filter(action__complete=False).annotate(action_count=Count('action'))
hidden_tags = Tag.objects.filter(visible=False).order_by('name').filter(action__complete=False).annotate(action_count=Count('action'))

I'd like to return them to an ajax function. I have to convert them to json, but I don't know how to include multiple querysets in the same json string.

score 3 · Answer 1 · edited Jun 07 '13 at 15:51

I know this thread is old, but using simplejson to convert django models doesn't work for many cases like decimals ( as noted by rebus above).

As stated in the django documentation, serializer looks like the better choice.

Django’s serialization framework provides a mechanism for “translating” Django models into other formats. Usually these other formats will be text-based and used for sending Django data over a wire, but it’s possible for a serializer to handle any format (text-based or not).

Django Serialization Docs

score 1 · Accepted Answer · edited Mar 11 '12 at 13:56

1

You can use Django's simplejson module. This code is untested though!

from django.utils import simplejson
dict = {
    'action_count': list(Action.objects.filter(complete=False, onhold=False).annotate(action_count=Count('name')).values()),
    'hold_count': list(Action.objects.filter(onhold=True, hold_criteria__isnull=False).annotate(action_count=Count('name')).values()),
    ...
}
return HttpResponse( simplejson.dumps(dict) )

I'll test and rewrite the code as necessary when I have the time to, but this should get you started.

edited Mar 11 '12 at 13:56

Davor Lucic

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answered Mar 10 '12 at 20:25

Simon Steinberger

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This won't actually work. You can't serialize a Django queryset like that, because the model instances themselves aren't serializable by the `json` module directly. – Daniel Roseman Mar 10 '12 at 22:09
Okay, thanks for the hint! I just re-wrote the code. Now actual lists of dictionaries are created on the fly. It should work - but it's still untested. Maybe it's not the most elegant way ... – Simon Steinberger Mar 11 '12 at 10:14
You could use [`values()`](https://docs.djangoproject.com/en/dev/ref/models/querysets/#values) or [`values_list()`](https://docs.djangoproject.com/en/dev/ref/models/querysets/#django.db.models.query.QuerySet.values_list) instead of building dictionaries that way, specially since if any of the fields are ForeingKey or something it would again return an unserializable object. `json.dumps(list(Model.object.filter().values()))` for example. – Davor Lucic Mar 11 '12 at 13:29
Not sure would this work for example with decimal fields though. – Davor Lucic Mar 11 '12 at 15:45
Thanks, all. I hacked this a bit, but got a working solution off the comments here. – Ed. Mar 12 '12 at 16:08

Convert multiple querysets to json in django

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