Flatten multi-level nested iterable (list, tuple, ...)

deep_flatten.py

"""Flatten multy-level nested iterable."""

from typing import Any, Iterable


def deep_flatten(data: Iterable[Any]) -> Iterable[float]:
    def inner(data):
        if isinstance(data, (int, float)):
            return [data]
        elif not data:
            return []
        first, *tail = data
        return inner(first) + inner(tail)

    return inner(data)


if __name__ == "__main__":
    tests = (
        ([], []),
        ([[[1, 2], [3, 4, 5]], [[[[6, 7]]]], [8], []], [1, 2, 3, 4, 5, 6, 7, 8]),
        ([[1, 2], [3, 4], [5]], [1, 2, 3, 4, 5]),
    )

    for test in tests:
        input, expected = test
        result = deep_flatten(input)
        assert result == expected

    print("PASSED!!!")