Processors

Processors allow us to take a value of a given type and transform it into another value of that type. Processors are most useful after type validation, but before predicates are checked. They tend to be more common on strings than any other type. Perhaps the most obvious use cases would be trimming whitespace or adjusting the case of a string:

from koda_validate import StringValidator, MaxLength, strip, upper_case, Valid

max_length_3_validator = StringValidator(
  MaxLength(3),
  preprocessors=[strip, upper_case]
)

assert max_length_3_validator(" hmm ") == Valid("HMM")

We see that the preprocessors stripped the whitespace from " hmm " and then transformed it to upper-case before the resulting value was checked against the MaxLength(3) Predicate.

Processors are very simple to write – see Extension for more details.