Frozenset

These types are subclasses of built-in frozenset type with some constraints on it.

InitHook

Type with special __init_hook__ method which is called on instantiation. It can be used to perform some additional checks on the value.

from valtypes.type.frozenset import InitHook
from valtypes.error.parsing import Base as ParsingError


class EvenNumbers(InitHook[int]):
    def __init_hook__(self) -> None:
        if any(n % 2 for n in self):
            raise ParsingError(f"{self.__class__.__name__} can't contain odd numbers")


EvenNumbers({2, 4, 6})  # passes
EvenNumbers({2, 3, 6})  # raises ParsingError

MinimumLength

Type for representing a frozenset that has a given minimum length. The minimum allowed length is stored in the __minimum_length__ attribute.

from typing import TypeVar

from valtypes.type.frozenset import MinimumLength


T_co = TypeVar("T_co", covariant=True)


class AtLeastTwoElements(MinimumLength[T_co]):
    __minimum_length__ = 2


AtLeastTwoElements({1, 2})  # passes
AtLeastTwoElements({1})  # raises valtypes.error.parsing.type.sized.MinimumLength

MaximumLength

Type for representing a frozenset that has a given maximum length. The maximum allowed length is stored in the __maximum_length__ attribute.

from typing import TypeVar

from valtypes.type.frozenset import MaximumLength


T_co = TypeVar("T_co", covariant=True)


class AtMostTwoElements(MaximumLength[T_co]):
    __maximum_length__ = 2


AtMostTwoElements({1, 2})  # passes
AtMostTwoElements({1, 2, 3})  # raises valtypes.error.parsing.type.sized.MaximumLength

NonEmpty

Type for representing a non-empty frozenset. It is a subclass of MinimumLength with __minimum_length__ set to 1.

from valtypes.type.frozenset import NonEmpty

NonEmpty({1})  # passes
NonEmpty()  # raises valtypes.error.parsing.type.sized.MinimumLength