Class IO

returns/io.py:31–229

Explicit container for impure function results. We also sometimes call it "marker" since once it is marked, it cannot be ever unmarked. There's no way to directly get its internal value. Note that ``IO`` represents a computation that never fails. Examples of such computat

class IO(  # type: ignore[type-var]
    BaseContainer,
    SupportsKind1['IO', _ValueType_co],
    io.IOLike1[_ValueType_co],
):
    """
    Explicit container for impure function results.

    We also sometimes call it "marker" since once it is marked,
    it cannot be ever unmarked.
    There's no way to directly get its internal value.

    Note that ``IO`` represents a computation that never fails.

    Examples of such computations are:

    - read / write to localStorage
    - get the current time
    - write to the console
    - get a random number

    Use ``IOResult[...]`` for operations that might fail.
    Like DB access or network operations.

    See also:
        - https://dev.to/gcanti/getting-started-with-fp-ts-io-36p6
        - https://gist.github.com/chris-taylor/4745921

    """

    __slots__ = ()

    _inner_value: _ValueType_co

    #: Typesafe equality comparison with other `Result` objects.
    equals = container_equality

    def __init__(self, inner_value: _ValueType_co) -> None:
        """
        Public constructor for this type. Also required for typing.

        .. code:: python

          >>> from returns.io import IO
          >>> assert str(IO(1)) == '<IO: 1>'

        """
        super().__init__(inner_value)

    def map(
        self,
        function: Callable[[_ValueType_co], _NewValueType],
    ) -> 'IO[_NewValueType]':
        """
        Applies function to the inner value.

        Applies 'function' to the contents of the IO instance
        and returns a new IO object containing the result.