Django serializers - add/update fields attribute value - json

Question

I'm using Django serializer for serializing the model data into JSON.
For example:- I have a model(CHECKTYPE) that contains one field 'types'.
Now 'types' contains comma(,) separated items like 'test, test1, test2'.
I'm using Django serializer like below (somewhere in view.py):
gettypes = CHECKTYPE.objects.all()
mytypes = serializers.serialize("json", gettypes)
return HttpResponse(mytypes, content_type="application/json")
This returns me a JSON on web page like below:
[{"model": "porttype.CHECKTYPE", "pk": "xyz00000005", "fields": {"types": "test, test1, test2"}}]
Now here I want to manipulate the fields attributes before serializing the data.
For example: I want to add one more attribute in fields 'lasttype' which will be last index of the list if I split the 'types' by comma.
lasttype = types.split(',')[-1]
so final json response should look like this:
[{"model": "porttype.CHECKTYPE", "pk": "xyz00000005", "fields": {"types": "test, test1, test2", "lasttype":"test2"}}]
I tried to do this like below but it's not working:
gettypes = CHECKTYPE.objects.all()
updated_types = []
for mtype in gettypes:
mtype.lasttype = mtype.types.split(',')[-1]
updated_types.append(mtype)
mytypes = serializers.serialize("json", updated_types)
return HttpResponse(mytypes, content_type="application/json")
But this is not working. It's giving me same JSON response and not showing the 'lasttype' attribute.
Please let me know if there is any possibility to achieve this.
Thanks,
Shashank

Answer 1

The best way to modify the response you are sending is by loading the json to dict then modifying the dict, then again json dumps the data for the response.

Answer 2

Instead of modifying fields before serializing, you should modify the fields after serializing.
import json
mytypes = json.loads(serializers.serialize("json", gettypes))
updated_types = []
for mytype in mytypes:
last_type = mytype['fields']['types'].split(',')[-1]
mytype['fields']['lasttype'] = last_type
updated_types.append(mytype)
return JsonResponse(updated_types)
By using JsonResponse you can directly json data without re-serializing the dict or list.
The expected data should be like this:
'[{"pk": "xyz00000005", "model": "porttype.CHECKTYPE", "fields": {"lasttype": " test2", "types": "test, test1, test2"}}]'