Method do

returns/future.py:1179–1220

Allows working with unwrapped values of containers in a safe way. .. code:: python >>> import anyio >>> from returns.future import FutureResult >>> from returns.io import IOSuccess, IOFailure >>> async def success() -> bool: ...

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

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

        .. code:: python

          >>> import anyio
          >>> from returns.future import FutureResult
          >>> from returns.io import IOSuccess, IOFailure

          >>> async def success() -> bool:
          ...     return await FutureResult.do(
          ...         first + second
          ...         async for first in FutureResult.from_value(2)
          ...         async for second in FutureResult.from_value(3)
          ...     ) == IOSuccess(5)

          >>> assert anyio.run(success) is True

          >>> async def failure() -> bool:
          ...     return await FutureResult.do(
          ...         first + second
          ...         async for first in FutureResult.from_value(2)
          ...         async for second in FutureResult.from_failure(3)
          ...     ) == IOFailure(3)

          >>> assert anyio.run(failure) is True

        See :ref:`do-notation` to learn more.

        """

        async def factory() -> Result[_NewValueType, _NewErrorType]:
            try:
                return Success(await anext(expr))
            except UnwrapFailedError as exc:
                return exc.halted_container  # type: ignore

        return FutureResult(factory())

    @classmethod
    def from_typecast(