Django JsonResponse converts numbers to string - django

Question

I'm using JsonResponse(status=200, data=<python_dict_with_data>) to return from my Django backend API. However, upon inspecting the result of this, all number values get converted to strings (these values are the value portion of the dict, not key). This creates a problem in the frontend receiving this response because now I have to parse them as integers to do formatting and lightweight calculations. Is there a way to prevent this conversion when returned from Django?
Or is there a way the response is parsed correctly in the frontend? I'm using Axios library in React in the frontend.

Answer 1

Is there a way to prevent this conversion when returned from Django?
The keys will indeed be transformed into strings, because ints as keys are illegal in JSON. Indeed, if you use a validator like JSONLint, you will see that {1: 1} is invalid JSON, whereas { "1": 1 } is valid JSON. The Python JSON encoder will thus fallback on converting the integers to strings, to still produce valid content.
If you have to do lightweight calculations, likely using these as keys is not a good idea. For example if you have data that looks like:
{ 1: 4, 2: 5 }
you might consider restructuring the data, for example to:
{ "data": [ {"key": 1, "value": 4}, {"key": 2, "value": 5} ] }
You can also return it as HTTP response, and do parsing at the JavaScript end, but likely that will only result in more trouble.
For Decimal numbers, it will also use a string. Django uses by default the DjangoJSONEncoder [Django-doc] which:
Decimal, Promise (django.utils.functional.lazy() objects), UUID:
A string representation of the object.
If we for example encode a Decimal, we see:
>>> djenc = DjangoJSONEncoder()
>>> djenc.encode({'a': Decimal('0.25')})
'{"a": "0.25"}'
You can subclass the encoder, and resolve the Decimal for example to a float, but note that this can result in loss of precision. This is exactly why a string is used: to ensure that no digits are lossed:
from django.core.serializers.json import DjangoJSONEncoder
from decimal import Decimal
class MyDjangoJSONEncoder(DjangoJSONEncoder):
def default(self, o):
if isinstance(o, Decimal):
return float(o)
return super().default(o)
this then produces:
>>> mydjenc = MyDjangoJSONEncoder()
>>> mydjenc.encode({'a': Decimal('0.25')})
'{"a": 0.25}'
You can then use this encoder in your JsonResponse:
from decimal import Decimal
def myview(request):
# …
JsonResponse(encoder=MyDjangoJSONEncoder, data={'a': Decimal('0.25')})