[Solved]-How to access serializer.data on ListSerializer parent class in DRF?

As mentioned in the comment i still think the exception could be because of the user field in BulkProductSerializer class, not really anything to do with ListSerializer

There might be another minor error (but important) in the serializer DRF as mentioned in the documentation here. Here is how to specify a list_serializer_class:

class CustomListSerializer(serializers.ListSerializer):
    ...

class CustomSerializer(serializers.Serializer):
    ...
    class Meta:
        list_serializer_class = CustomListSerializer

Note that it’s specified inside of the Meta class, not outside. So i think in your code, it will not understand to switch to the List Serializer with many=True. That should cause the not-updating problem.

Update – Add example for updating nested list serializer

It seems that the question was more about a generic way to implement updating for nested List Serializer rather than the actual error. Therefore, i will try to provide a sample code.

Some notes:

• If we use ModelViewSet, the list route won’t allow PUT or PATCH, so neither update nor partial_update will be called (reference). Therefore i use POST directly, this is much simpler.
• If you want to use PUT/PATCH, then see this answer here
• We can always add a query parameter like allow_update or partial directly to the Post request to differentiate between POST/PUT/PATCH
• Instead of using uuid like the question i will use the normal id, it should be very much the same

It was rather simple

For reference, models look like this:

class Product(models.Model):
    name = models.CharField(max_length=200)
    user = models.ForeignKey(User, null=True, blank=True)

    def __unicode__(self):
        return self.name

Step 1: Make sure serializer change to ListSerializer

class ProductViewSet(viewsets.ModelViewSet):
    serializer_class = ProductSerializer
    queryset = Product.objects.all()

    def get_serializer(self, *args, **kwargs):
        # checking for post only so that 'get' won't be affected
        if self.request.method.lower() == 'post':
            data = kwargs.get('data')
            kwargs['many'] = isinstance(data, list)
        return super(ProductViewSet, self).get_serializer(*args, **kwargs)

Step 2: Implement the ListSerializer by overriding create function

class ProductListSerializer(serializers.ListSerializer):
    def create(self, validated_data):
        new_products = [Product(**p) for p in validated_data if not p.get('id')]
        updating_data = {p.get('id'): p for p in validated_data if p.get('id')}
        # query old products
        old_products = Product.objects.filter(id__in=updating_data.keys())
        with transaction.atomic():
            # create new products
            all_products = Product.objects.bulk_create(new_products)
            # update old products
            for p in old_products:
                data = updating_data.get(p.id, {})
                # pop id to remove
                data.pop('id')
                updated_p = Product(id=p.id, **data)
                updated_p.save()
                all_products.append(updated_p)
        return all_products


class ProductSerializer(serializers.ModelSerializer):
    user = serializers.SlugRelatedField(slug_field='username', queryset=User.objects.all())
    id = serializers.IntegerField(required=False)

    class Meta:
        model = Product
        fields = '__all__'
        list_serializer_class = ProductListSerializer

Your Error has nothing to do with ListSerializer, but a problem getting field user:

KeyError: "Got KeyError when attempting to get a value for field user on serializer BulkProductSerializer.

The serializer field might be named incorrectly and not match any attribute or key on the OrderedDict instance.

Original exception text was: ‘fk_user’."

Make sure your Product model has a fk_user field.

You also have defined user field on BulkProductSerializer as writable but have not told the serializer how to handle it…

The easiest way to correct this is to use a SlugRelatedField:

class BulkProductSerializer(serializers.ModelSerializer):

    list_serializer_class = CustomProductListSerializer

    user = serializers.SlugRelatedField(
                            slug_field='username',
                            queryset=UserModel.objects.all(),
                            source='fk_user'
    )

    class Meta:
        model = Product
        fields = (
            'user',
            'uuid',
            'product_code',
            ...,
        )

This should handle nicely errors, for example when username does not exist…

Remove source if you are using Django auth model and set read_only=True.

user = serializers.CharField(read_only=True)

Hope this works for you