Method do

returns/io.py:647–677

Allows working with unwrapped values of containers in a safe way. .. code:: python >>> from returns.io import IOResult, IOFailure, IOSuccess >>> assert IOResult.do( ... first + second ... for first in IOSuccess(2) ...

(
        cls,
        expr: Generator[_NewValueType, None, None],
    )

    @classmethod
    def do(
        cls,
        expr: Generator[_NewValueType, None, None],
    ) -> 'IOResult[_NewValueType, _NewErrorType]':
        """
        Allows working with unwrapped values of containers in a safe way.

        .. code:: python

          >>> from returns.io import IOResult, IOFailure, IOSuccess

          >>> assert IOResult.do(
          ...     first + second
          ...     for first in IOSuccess(2)
          ...     for second in IOSuccess(3)
          ... ) == IOSuccess(5)

          >>> assert IOResult.do(
          ...     first + second
          ...     for first in IOFailure('a')
          ...     for second in IOSuccess(3)
          ... ) == IOFailure('a')

        See :ref:`do-notation` to learn more.
        This feature requires our :ref:`mypy plugin <mypy-plugins>`.

        """
        try:
            return IOResult.from_value(next(expr))
        except UnwrapFailedError as exc:
            return IOResult.from_result(exc.halted_container)  # type: ignore

    @classmethod
    def from_typecast(