何回でも列挙できるイテレータを作るクラス

iterator.py

class MemoizedIterator:
    def __init__(self, iterable):
        self.iterator = iterable
        self.elements = []
    def __iter__(self):
        for i in self.elements:
            yield i
        for i in self.iterator:
            self.elements.append(i)
            yield i