Method collect

returns/iterables.py:96–156

Transforms an iterable of containers into a single container. Quick example for regular containers: .. code:: python >>> from returns.io import IO >>> from returns.iterables import Fold >>> items = [IO(1), IO(2)] >>> assert Fold.co

(
        cls,
        iterable: Iterable[
            KindN[_ApplicativeKind, _FirstType, _SecondType, _ThirdType],
        ],
        acc: KindN[
            _ApplicativeKind,
            'tuple[_FirstType, ...]',
            _SecondType,
            _ThirdType,
        ],
    )

    @kinded
    @classmethod
    def collect(
        cls,
        iterable: Iterable[
            KindN[_ApplicativeKind, _FirstType, _SecondType, _ThirdType],
        ],
        acc: KindN[
            _ApplicativeKind,
            'tuple[_FirstType, ...]',
            _SecondType,
            _ThirdType,
        ],
    ) -> KindN[
        _ApplicativeKind,
        'tuple[_FirstType, ...]',
        _SecondType,
        _ThirdType,
    ]:
        """
        Transforms an iterable of containers into a single container.

        Quick example for regular containers:

        .. code:: python

          >>> from returns.io import IO
          >>> from returns.iterables import Fold

          >>> items = [IO(1), IO(2)]
          >>> assert Fold.collect(items, IO(())) == IO((1, 2))

        If container can have failed values,
        then this strategy fails on any existing failed like type.

        It is enough to have even a single failed value in iterable
        for this type to convert the whole operation result to be a failure.
        Let's see how it works:

        .. code:: python

          >>> from returns.result import Success, Failure
          >>> from returns.iterables import Fold

          >>> empty = []
          >>> all_success = [Success(1), Success(2), Success(3)]
          >>> has_failure = [Success(1), Failure('a'), Success(3)]
          >>> all_failures = [Failure('a'), Failure('b')]

          >>> acc = Success(())  # empty tuple

          >>> assert Fold.collect(empty, acc) == Success(())
          >>> assert Fold.collect(all_success, acc) == Success((1, 2, 3))
          >>> assert Fold.collect(has_failure, acc) == Failure('a')
          >>> assert Fold.collect(all_failures, acc) == Failure('a')

        If that's now what you need, check out
        :meth:`~AbstractFold.collect_all`
        to force collect all non-failed values.