Python lazy zip gen

lazy_zip

def zip_gen(list_key, list_value):
    '''
    >>> dict([(a,b) for (a,b) in zip_gen([1,2,3,4], ['a','b','c','d'])])
    {1: 'a', 2: 'b', 3: 'c', 4: 'd'}
    >>> dict([(a,b) for (a,b) in zip_gen([1,2], ['a','b','c','d'])])
    {1: 'a', 2: 'b'}
    >>> dict([(a,b) for (a,b) in zip_gen([1,2,3,4], ['a'])])
    {1: 'a', 2: None, 3: None, 4: None}

    '''

    iter_key = list_key.__iter__()
    iter_value = list_value.__iter__()
    while True:
        try:
            key = iter_key.next()
            try:
                value = iter_value.next()
                yield(key, value)
            except StopIteration as vse:
                    yield (key, None)
        except StopIteration as kse:
            return


if __name__ == '__main__':
    import doctest
    doctest.testmod()