[Django]-Dynamically exclude or include a field in Django REST framework serializer

Creating a new serializer is the way to go. By conditionally removing fields in a serializer you are adding extra complexity and making you code harder to quickly diagnose. You should try to avoid mixing the responsibilities of a single class.

Following basic object oriented design principles is the way to go.

QuestionWithTopicView is a QuestionWithoutTopicView but with an additional field.

class QuestionSerializer(serializers.Serializer):
        id = serializers.CharField()
        question_text = QuestionTextSerializer()
        topic = TopicSerializer()

class TopicQuestionSerializer(QuestionSerializer):
       topic = TopicSerializer()

You can set fields and exclude properties of Meta

Here is an Example:

class DynamicFieldsModelSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        exclude = ['id', 'email', 'mobile']

    def __init__(self, *args, **kwargs):
        super(DynamicFieldsModelSerializer, self).__init__(*args, **kwargs)
        #  @note: For example based on user,  we will send different fields
        if self.context['request'].user == self.instance.user:
            # Or set self.Meta.fields = ['first_name', 'last_name', 'email', 'mobile',]
            self.Meta.exclude = ['id']

Extending above answer to a more generic one

class QuestionSerializer(serializers.Serializer):
    def __init__(self, *args, **kwargs):
        fields = kwargs.pop('fields', None)
        super(QuestionSerializer, self).__init__(*args, **kwargs)
        if fields is not None:
            allowed = set(fields.split(','))
            existing = set(self.fields)
            for field_name in existing - allowed:
                self.fields.pop(field_name)

class QuestionWithoutTopicView(generics.RetrieveAPIView):
    def get_serializer(self, *args, **kwargs):
        kwargs['context'] = self.get_serializer_context()
        fields = self.request.GET.get('display')
        serializer_class = self.get_serializer_class()
        return serializer_class(fields=fields,*args, **kwargs)
    def get_serializer_class(self):
        return QuestionSerializer
    

Now we can give a query parameter called display to output any custom display format http://localhost:8000/questions?display=param1,param2

You can use to representation method and just pop values:

def to_representation(self, instance):
    """Convert `username` to lowercase."""
    ret = super().to_representation(instance)
    ret.pop('username') = ret['username'].lower()
    return ret

you can find them here

https://www.django-rest-framework.org/api-guide/serializers/#overriding-serialization-and-deserialization-behavior