def index_iterator(shape):
    """Iterates over the indexes of a multi-dimensional array of a specified shape.

    The last index changes most rapidly.
    :param shape: sequence of array dimensions
    :return: yields tuples of array indexes
    """
    dim = len(shape)
    idx = [0] * dim
    num_iterations = 1
    for j in range(0, dim):
        num_iterations *= shape[j]
    for iterations in range(num_iterations):
        yield tuple(idx)
        for j in range(dim - 1, -1, -1):
            idx[j] += 1
            if idx[j] < shape[j]:
                break
            idx[j] = 0
