Django Rest Framework：如何序列化列表列表？

Question

How to serialize list of list of Floats using Django Rest serializers?

My data is ( repr of my list of object):

[{
    'id': '413',
    'data': [
        [None, 32.33125, None, None],
        [None, 37.96, 48.70112359550562, 66.118],
        [None, None, 58.06576923076923, 77.31023809523809],
        [None, None, None, 110.0075],
        [None, None, None, 139.89]
    ]
}, {
    'id': '406',
    'data': [
        [None, 35.33125, None, None],
        [None, 37.96, 43.123, 66.118],
        [None, None, 58.12, 72,123],
        [None, None, None, 119.000234],
        [None, None, None, 139.89]
    ]
}]

For users trying to propose different approach, I need to explain that I need serializer class because I want to use generics.ListAPIView and I need to setup serializer_class property.

Answer 1

You must create Field class that will work with Null values:

class FixedFloatField(serializers.FloatField):
    def to_internal_value(self, data):
        if data is None:
            return data
        return super().to_internal_value(data)

    def to_representation(self, value):
        if value is None:
            return value
        return super().to_representation(value)

(because standard one throws TypeError: float() argument must be a string or a number, not 'NoneType' )

Now use this Serializer (the trick is to use ListField ):

class SearchResultSerializer(serializers.Serializer):
    id = serializers.IntegerField()
    data = serializers.ListField(
        child=serializers.ListField(
            child=FixedFloatField(
                allow_null=True,
                required=False,
                default=None
            )
        )
    )

Answer 2

You can use the biult-in json module.

data = [{
    'id': '413',
    'data': [
        [None, 32.33125, None, None],
        [None, 37.96, 48.70112359550562, 66.118],
        [None, None, 58.06576923076923, 77.31023809523809],
        [None, None, None, 110.0075],
        [None, None, None, 139.89]
    ]
}, {
    'id': '406',
    'data': [
        [None, 35.33125, None, None],
        [None, 37.96, 43.123, 66.118],
        [None, None, 58.12, 72,123],
        [None, None, None, 119.000234],
        [None, None, None, 139.89]
    ]
}]

import json
json_data = json.dumps(data)

You can mix this with a DRF view:

from rest_framework.response import Response
...
json_data = json.dumps(data)
return Response(json_data)

EDIT

To use ListAPIView

assuming your data are coming from a model named Mymodel

# Serializer
from rest_framework import serializers

class MymodelSerializer(serializers.ModelSerializer):

    class Meta:
        model = Mymodel

# View
from rest_framework import generics

class MymodelList(generics.ListAPIView):

    queryset = Mymodel.objects.filter(whatever=whatever)

    def list(self, request):
        # Note the use of `get_queryset()` instead of `self.queryset`
        queryset = self.get_queryset()
        serializer = UserSerializer(queryset, many=True)
        return Response(serializer.data)

Taken from DRF docs