Django REST to_representation: Have serializer fields appear last

Question

I have the following serializer class:

class DataLocationSerializer(QueryFieldsMixin, serializers.ModelSerializer):

    def create(self, validated_data):
        pass

    def update(self, instance, validated_data):
        pass

    class Meta:
        model = MeasurementsBasic
        fields = ['temp', 'hum', 'pres', 'co', 'no2',
                            'o3', 'so2']

    def to_representation(self, instance):
        representation = super().to_representation(instance)
        representation['timestamp'] = instance.time_received

        return representation

The data is returned in a JSON file structured like this:

{
    "source": "ST",
    "stations": [
        {
            "station": "ST1",
            "data": [
                {
                    "temp": -1.0,
                    "hum": -1.0,
                    "pres": -1.0,
                    "co": -1.0,
                    "no2": -1.0,
                    "o3": -1.0,
                    "so2": null,
                    "timestamp": "2021-07-04T21:00:03"                  
                }
            ]
        }
    ]
}

How can i make it so the timestamp appears before the serializer's fields?

Answer 1

Create a new dictionary:

def to_representation(self, instance):
    representation = super().to_representation(instance)
    return {'timestamp': instance.time_received, **representation }