Using custom validation for built in types

Question

I'm looking to validate the datetime type with custom validator, rather than the built in one.

The code looks like this:

        schema_text = """
            run_date:
                type: datetime
                required: true
            """
        s.schema = yaml.load(schema_text)

        s.validate(yaml.load("run_date: 2017-01-01T00:00+00:00:00"))

I could do this using checks_with: my_custom_validator, which would be ok but I'm hoping to open these schemas up to the public, so asking them all to contribute to them would be a bother. I think this could also be done using a normalizer but, again, I'd prefer not to munge with the input.

Any suggestions here? The dateutil parser is exactly what I want to use.

Answer 1

As your input data is a string which represents a datetime in ISO 8601 format, you can use two approaches without any customization.

Either (try to) convert the string to a datetime.datetime object:

from datetime import datetime

schema = {
    "run_date": {"coerce": datetime.fromisoformat}
}

This would need to be validated with normalization and either cause an error or cast the run_date field's value into a datetime.datetime object.

If you want to stick with a string as data type, use the regex rule:

schema = {
    "run_date": {"type": "string", "regex": r"\d{4}-\d\d-\d\d-etc.pp."}
}