"""Useful functions for list operations"""
import collections

def flatten(inputList):
    """Return a flattened genertor from an input list

        Usage:
            inputList = [['a'], ['b', 'c', 'd'], [['e']], ['f']]
            list(flatten(inputList))
            >> ['a', 'b', 'c', 'd', 'e', 'f']
    """
    for el in inputList:
        if isinstance(el, collections.Iterable) and not isinstance(el, basestring):
            for sub in flatten(el):
                yield sub
        else:
            yield el

def unflatten(guide, falttenedInput):
    """Unflatten a falttened generator
        guide: A guide list to follow the structure
        falttenedInput: A flattened iterator object

        Usage:
            guide = [["a"], ["b","c","d"], [["e"]], ["f"]]
            inputList = [0, 1, 2, 3, 4, 5, 6, 7]
            unflatten(guide, iter(inputList))
            >> [[0], [1, 2, 3], [[4]], [5]]
    """
    return [unflatten(subList, falttenedInput) if isinstance(subList, list) else next(falttenedInput) for subList in guide]