[question] Skip missing fields instead of default values

I have tried to find answer myself but failed - it seems it is not supported right now.

In case if I’ve missed it: is it possible to skip missing fields instead of assigning default values during serialization?

I will try to describe it in example:

some_data = dict(
    first_name='Joe',
    age=20,
)


class TestSchema(Schema):
    first_name = String()
    family_name = String()
    age = Integer()


schema = TestSchema()
print(schema.dump(some_data).data)

Current result: OrderedDict([('first_name', u'Joe'), ('family_name', ''), ('age', 20)]) Desired result: OrderedDict([('first_name', u'Joe'), ('age', 20)])

Of course it is possible to filter the result afterwards. Although it is quite tricky due to the different default values (i.e. for strings, integers) but possible and I’ve already done it.

I am just curious if I’ve missed some core functionality.

[Behoston]

1. Recursive

class NotNoneSchemaBase:
    @post_dump
    def clear_none(self, data):
        result = {}
        for k, v in data.items():
            if v is None:
                continue
            elif isinstance(v, dict):
                result[k] = self.clear_none(v)
            else:
                result[k] = v
        return result

[sloria]

An update: skipping missing values is now the default behavior in marshmallow 2.0.0: https://marshmallow.readthedocs.org/en/latest/upgrading.html#default-values

For this reason, I think I’m going to go ahead and deprecate the skip_missing option.