Django-REST framework restore_object attrs parameters

Question

Finding the Django-REST framework documentation to be, despite how lengthy it is, still too light on background for me.

What does the restore_object method's attrs function do?

instance.title = attrs.get('title', instance.title)

What does the second argument stand for, and how would I go about looking for what this would mean in the future in the docs?

Also not sure what the double asterisks in return Snippet(**attrs) means. This is different from **keywArgs ? What arguments are being passed back to the deserialized Snippet object?

In another section of the docs, I see in restore_object() instance.title = attrs['title'] which I hope one might be able to see my confusion.

thank you

class SnippetSerializer(serializers.Serializer):
    pk = serializers.Field()  # Note: `Field` is an untyped read-only field.
    title = serializers.CharField(required=False,
                                  max_length=100)
    code = serializers.CharField(widget=widgets.Textarea,
                                 max_length=100000)
    linenos = serializers.BooleanField(required=False)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES,
                                       default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES,
                                    default='friendly')

    def restore_object(self, attrs, instance=None):
        """
        Create or update a new snippet instance.
        """
        if instance:
            # Update existing instance
            instance.title = attrs.get('title', instance.title)
            instance.code = attrs.get('code', instance.code)
            instance.linenos = attrs.get('linenos', instance.linenos)
            instance.language = attrs.get('language', instance.language)
            instance.style = attrs.get('style', instance.style)
            return instance

        # Create new instance
        return Snippet(**attrs)

Answer 1

I've updated the documentation slightly in an aim to make that more clear...

http://django-rest-framework.org/tutorial/1-serialization.html#creating-a-serializer-class

The method now reads...

def restore_object(self, attrs, instance=None):
    """
    Create or update a new snippet instance, given a dictionary
    of deserialized field values.

    Note that if we don't define this method, then deserializing
    data will simply return a dictionary of items.
    """
    if instance:
        # Update existing instance
        instance.title = attrs.get('title', instance.title)
        instance.code = attrs.get('code', instance.code)
        instance.linenos = attrs.get('linenos', instance.linenos)
        instance.language = attrs.get('language', instance.language)
        instance.style = attrs.get('style', instance.style)
        return instance

    # Create new instance
    return Snippet(**attrs)

The **attrs style is using Python's standard keyword expansion. See here for a good explanation.

It'll end up as the equivalent of Snippet(title=attrs['title'], code=attrs['code'], ...)

Hope that helps!