How to override exception messages in django rest framework

Question

I am using django class based view and rest framework

object = self.get_object()

In Detail view if object does not exist and i do get reque

Answer 1

You could create a custom exception class as below, and it would raise APIException with a custom message and custom status_code

from rest_framework.serializers import ValidationError
from rest_framework import status



class CustomAPIException(ValidationError):
    """
    raises API exceptions with custom messages and custom status codes
    """
    status_code = status.HTTP_400_BAD_REQUEST
    default_code = 'error'

    def __init__(self, detail, status_code=None):
        self.detail = detail
        if status_code is not None:
            self.status_code = status_code

and in your views,

from rest_framework import status

try:
    obj = self.get_object()
except:
    raise CustomAPIException("This object does not exist", status_code=status.HTTP_404_NOT_FOUND)

The response will be like this
{"detail": "This object does not exist"}

NOTE

the detail parameter of CustomAPIException class takes str,list and dict objects. If you provide a dict object, then it will return that dict as exception response

UPDATE

As @pratibha mentioned, it's not possible to produce desired output if we use this exception class in Serializer's validate() or validate_xxfieldName() methods.

Why this behaviour ?
I wrote a similar answer in SO, here Django REST Framework ValidationError always returns 400

How to obtain desired output within the serializer's validate() method?
Inherit CustomAPIException from rest_framework.exceptions.APIException instead of from rest_framework.serializers.ValidationError
ie,

from rest_framework.exceptions import APIException


class CustomAPIException(APIException):
    # .... code