Question

How can I validate following data structure using colander library?

[
    {
        'bar': ['a', 'b', 'c'],
        'variable2': ['b', 'c'],
        'foo': ['a', 'c'],
    },
    {
        'something': ['foo', 'bar'],
    },
]

The problem is that these mapping can have any number of key-value pairs, and keys namespace is not restricted. I also want to make sure that each key is a string and each value is a sequence of strings.

I could use Mapping(unknown='preserve'), but it won’t validate the types.

Answer 1

Looking at the documentation, I don’t think you can. You could get around the limitation you mentioned by defining your own validator:

A validator is a callable which accepts two positional arguments: node and value. It returns None if the value is valid. It raises a colander.Invalid exception if the value is not valid.