Leaving this for my own record. how to implement a lazy eval loop in python

lazy_eval_looping.py

import unittest


class Container:
    def __init__(self, items):
        self.__cur = 0
        self.__items = items

    def __iter__(self):
        self.__cur = 0
        return self

    def next(self):
        if self.__cur + 1 > len(self.__items):
            raise StopIteration
        self.__cur += 1
        return '%s * 2' % self.__items[self.__cur - 1]


class Test(unittest.TestCase):
    def test(self):
        container = Container([0, 1])
        for idx, item in enumerate(container):
            self.assertEqual(item, '%s * 2' % idx)


if __name__ == '__main__':
    unittest.main()