Maps

For dictionaries with consistent key/value types, you can use MapValidator.

from koda_validate import (MapValidator, StringValidator, IntValidator, KeyValErrs, MapErr,
                           MinKeys, MaxKeys, Valid, Invalid, PredicateErrs, TypeErr)

validator = MapValidator(key=StringValidator(),
                         value=IntValidator(),
                         predicates=[MinKeys(1), MaxKeys(3)])


assert validator({"a": 1, "b": 2}) == Valid({'a': 1, 'b': 2})

assert validator({}) == Invalid(PredicateErrs([MinKeys(1)]), {}, validator)

assert validator({"a": "not an int"}) == Invalid(
    MapErr({'a': KeyValErrs(key=None,
                            val=Invalid(TypeErr(int), 'not an int', IntValidator()))}),
    {'a': 'not an int'},
    validator
)

Mypy will infer that the type of valid data returned from validator above will be Dict[str, int].