Answers by Sentry

Creating a JSON response using Django and Python

Gareth D.

The Problem

You want to pass a JSON response from your Django backend to use with AJAX or a frontend web framework.

The Solution

Django (since version 1.7) provides a JsonResponse object which converts a Python dictionary into JSON. It also works with other Python data structures, such as arrays, but if you’re using anything that’s not a dictionary you need to explicitly set safe=False. In this case, you should also be careful that your application isn’t ever going to return more or different data to the frontend than you expect.

In your views.py file, you can return JSON as demonstrated in the following code. The first view uses a simple dictionary, while the second one returns an array, so we set safe=False.

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from django.http import JsonResponse

def index(request):
    my_dictionary = {"a": 1, "b": 2}
    return JsonResponse(my_dictionary)

def index2(request):
    my_array = [("a", 1), ("b", 2)]
    return JsonResponse(my_array, safe=False)

The index function above will return {"a": 1, "b": 2} while index2 will return [["a", 1], ["b", 2]] (note the round brackets are converted to square brackets to conform with standard JSON).

Serialization and escaping

If you use JsonResponse to return an entire object, Django will escape the double quotation marks in all fields. For example, if you have the following object:

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from django.core import serializers
from django.http import JsonResponse
from django.db import models

class MyTrickyObject(models.Model):
    quotes = models.CharField(max_length=100)

def index(request):
    MyTrickyObject.objects.all().delete()
    all_objs = MyTrickyObject.objects.all()
    tricky_obj = MyTrickyObject(quotes='"this is a quoted string"')
    tricky_obj.save()
    tricky_objects = MyTrickyObject.objects.all()
    data = serializers.serialize('json', all_objs)
    return JsonResponse(data, safe=False)

Then the response will be:

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"[{\"model\": \"sandboxapp.mytrickyobject\", \"pk\": 21, \"fields\": {\"quotes\": \"\\\"this is a quoted string\\\"\"}}]"

Note how every field includes the (escaped) double quotes, and the actual quotes in the quotes field are now double escaped. Instead, you can use an HttpResponse and content_type='application/json' to get just the fields without the quotes:

Click to Copy
from django.core import serializers
from django.http import HttpResponse
from django.db import models

class MyTrickyObject(models.Model):
    quotes = models.CharField(max_length=100)

def index(request):
    MyTrickyObject.objects.all().delete()
    all_objs = MyTrickyObject.objects.all()
    tricky_obj = MyTrickyObject(quotes='"this is a quoted string"')
    tricky_obj.save()
    tricky_objects = MyTrickyObject.objects.all()
    data = serializers.serialize('json', all_objs)
    return HttpResponse(data, content_type='application/json')

Now the response will be:

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[{"model": "sandboxapp.mytrickyobject", "pk": 22, "fields": {"quotes": "\"this is a quoted string\""}}]

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