How to create a "type-agnostic" SchemaNode in colander

Question

I'm trying to use colander to define a SchemaNode that could have any type. I'd like it to just take whatever was deserialized from the JSON and pass it along. Is that possible?

class Foo(colander.MappingSchema):
    name = colander.SchemaNode(colander.String(), validator=colander.Length(max=80))
    value = colander.SchemaNode(??) # should accept int, float, string...

Answer 1

Those Colander types derive from SchemaType and implement the methods that actually do the serialisation and deserialisation.

The only way I can think of to do this is write your own implementation of SchemaType that is essentially a wrapper that tests the value and applies one of the types defined in Colander.

I don't think it would be that hard, just not pretty.

Edit: Here's a scratch example. I haven't tested it, but it conveys the idea.

class AnyType(SchemaType):

    def serialize(self, node, appstruct):
        if appstruct is null:
            return null

        impl = colander.Mapping()  # Or whatever default.
        t = type(appstruct)

        if t == str:
            impl = colander.String()
        elif t == int:
            impl = colander.Int()
        # Test the others, throw if indeterminate etc.

        return impl.serialize(node, appstruct)

    def deserialize(self, node, cstruct):
        if cstruct is null:
            return null

        # Test and return again.

Answer 2

I only needed the deserialization, so I used a simplified version of SpiritMachine's answer:

class AnyType(colander.SchemaType):
    def deserialize(self, node, cstruct):
        return cstruct

I might add something in later for date/datetime detection.