JSON schema can also be used to validate YAML. This presumes that you might want to use jsonschema and yaml together.

StrictYAML was inspired by the frustration of trying to use pyyaml with pykwalify, in fact.

Loss of line numbers

Because parsing first with pyyaml and then passing the result to pykwalify loses line numbers, validation errors lose the line number where the validation error occurred.

This makes tracking down the location of errors tricky. If a schema is a little repetitive it can make tracking down the exact location of the error hellish.

Simpler errors in StrictYAML

StrictYAML has an emphasis on the friendliness of schema validation errors. Ideally every schema validation error should be extremely obvious and show only the information necessary.

StrictYAML schemas are more flexible

Because schemas are written in python and strictyaml allows revalidation, strictyaml schemas are much more flexible:

Example:

from strictyaml import load, Seq, Enum
import pycountry    # updated list of country codes


load(
    strictyaml_string,
    Map(
        {
            "countries": Seq(Enum([country.alpha_2 for country in pycountry.countries]))
        }
    )
)