Output Django queryset as JSON
DjangoJsonListviewDjango Problem Overview
I want to serialize my queryset, and I want it in a format as this view outputs:
class JSONListView(ListView):
queryset = Users.objects.all()
def get(self, request, *args, **kwargs):
return HttpResponse(json.dumps({'data': [['bar','foo','bar','foo'],['foo','bar','foo','bar']]}, indent=4), content_type='application/json')
I simply don't know how to output the queryset instead of the manual data in the example.
I've tried
json.dumps({"data": self.get_queryset()})
and
serializers.serialize("json", {'data': self.get_queryset()})
but it wont work. What am I doing wrong? Do I need to make a custom JSON Encoder?
Django Solutions
Solution 1 - Django
You can use JsonResponse with values. Simple example:
from django.http import JsonResponse
def some_view(request):
data = list(SomeModel.objects.values()) # wrap in list(), because QuerySet is not JSON serializable
return JsonResponse(data, safe=False) # or JsonResponse({'data': data})
Or another approach with Django's built-in serializers:
from django.core import serializers
from django.http import HttpResponse
def some_view(request):
qs = SomeModel.objects.all()
qs_json = serializers.serialize('json', qs)
return HttpResponse(qs_json, content_type='application/json')
In this case result is slightly different (without indent by default):
[ { "model": "some_app.some_model", "pk": 1, "fields": { "name": "Elon", "age": 48, ... } }, ...]
I have to say, it is good practice to use something like marshmallow to serialize queryset.
...and a few notes for better performance:
-
use pagination if your queryset is big;
-
use
objects.values()
to specify list of required fields to avoid serialization and sending to client unnecessary model's fields (you also can passfields
toserializers.serialize
);
Solution 2 - Django
It didn't work, because QuerySets are not JSON serializable.
-
In case of
json.dumps
you have to explicitely convert your QuerySet to JSON serializable objects:class Model(model.Model): def as_dict(self): return { "id": self.id, # other stuff }
And the serialization:
dictionaries = [ obj.as_dict() for obj in self.get_queryset() ]
return HttpResponse(json.dumps({"data": dictionaries}), content_type='application/json')
2) In case of serializers. Serializers accept either JSON serializable object or QuerySet, but a dictionary containing a QuerySet is neither. Try this:
serializers.serialize("json", self.get_queryset())
Read more about it here:
Solution 3 - Django
For a efficient solution, you can use .values() function to get a list of dict objects and then dump it to json response by using i.e. JsonResponse (remember to set safe=False
).
Once you have your desired queryset object, transform it to JSON response like this:
...
data = list(queryset.values())
return JsonResponse(data, safe=False)
You can specify field names in .values()
function in order to return only wanted fields (the example above will return all model fields in json objects).
Solution 4 - Django
To return the queryset you retrieved with queryset = Users.objects.all(),
you first need to serialize them.
Serialization is the process of converting one data structure to another. Using Class-Based Views, you could return JSON like this.
from django.core.serializers import serialize
from django.http import JsonResponse
from django.views.generic import View
class JSONListView(View):
def get(self, request, *args, **kwargs):
qs = User.objects.all()
data = serialize("json", qs)
return JsonResponse(data)
This will output a list of JSON. For more detail on how this works, check out my blog article How to return a JSON Response with Django. It goes into more detail on how you would go about this.
Solution 5 - Django
If the goal is to build an API that allow you to access your models in JSON format I recommend you to use the django-restframework
that is an enormously popular package within the Django community to achieve this type of tasks.
It include useful features such as Pagination, Defining Serializers, Nested models/relations and more. Even if you only want to do minor Javascript tasks and Ajax calls I would still suggest you to build a proper API using the Django Rest Framework instead of manually defining the JSON response.
Solution 6 - Django
Another way to turn queryset into JSON, is appending necessary elements to an empty list with loop. It provides to design customizable JSON.
queryset = Users.objects.all()
output = []
for query in queryset:
output.append('id': query.id, 'name': query.name, etc...)
return JSONResponse(output, safe=False)
Solution 7 - Django
Try this:
class JSONListView(ListView):
queryset = Users.objects.all()
def get(self, request, *args, **kwargs):
data = {}
data["users"] = get_json_list(queryset)
return JSONResponse(data)
def get_json_list(query_set):
list_objects = []
for obj in query_set:
dict_obj = {}
for field in obj._meta.get_fields():
try:
if field.many_to_many:
dict_obj[field.name] = get_json_list(getattr(obj, field.name).all())
continue
dict_obj[field.name] = getattr(obj, field.name)
except AttributeError:
continue
list_objects.append(dict_obj)
return list_objects
Solution 8 - Django
from django.http import JsonResponse
def SomeFunction():
dict1 = {}
obj = list( Mymodel.objects.values() )
dict1['data']=obj
return JsonResponse(dict1)
Try this code for Django