Combination.py

class Combination:
    def __init__(self, elements, len_list):
        self.elements = elements
        self.len_list = len_list

    def __len__(self):
        return pow(len(self.elements), self.len_list)

    def __iter__(self):
        for element in self.elements:
            if (self.len_list > 1):
                for sub_combination in Combination(self.elements, self.len_list - 1):
                    yield [element] + sub_combination
            else:
                yield [element]