Django Rest Framework (DRF)

Serialize / Deserialize

Remove Fields from Serializer Output

There are cases when we need to remove one or more fields from Django Rest Framework serializer’s output. For example:

  • Remove personal information for users without AuthorizationError

  • Feature toggles - we want certain information to be available in the output based on a feature toggle (flag).

Override the default to_representation method to drop the field from the output:

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User

    def to_representation(self, instance):
        representation = super().to_representation(instance)
        representation.pop('salary')
        return representation

In this example, the salary field is removed from the serializer output.

The behavior could be extracted into a function:

def drop_fields(representation:dict, fields, error_handler=None):
    """Drop a one or more fields from serializer representation"""
    fields = (fields,) if type(fields) == str else fields
    for field_name in fields:
        try:
            representation.pop(field_name)
        except Exception as error:
            if error_handler:
                error_handler(error)
            else:
                raise
    return representation

Using the function our class becomes:

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User

    def to_representation(self, instance):
        representation = drop_fields(super().to_representation(instance), 'salary')
        return representation

In case field is already missing in the output, KeyError will be raised. This might not be the desired behavior. We might want to ignore missing fields. For such situations we have provided the error_handler argument for the drop_fields function.

def ignore_errors(errors:list):
    def error_handler(error:Exception):
        """If error is instance of given classes ignore it or raise the error otherwise"""
        if not isinstance(error, errors):
            raise error
    return error_handler

class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User

    def to_representation(self, instance):
        representation = drop_fields(
            super().to_representation(instance),
            'salary',
            ignore_errors(KeyError),
        )
        return representation

Both functions has been added to the pygems.core.shortcuts module.