>>> >>> s = [] >>> s.append(((b, c) for b, c in a)) >>> s [<generator object <genexpr> at 0x0000019FC3F863C0>] >>> TIA for any insights. Replace "append" above with "extend" and observe the results. Then ponder the difference between append and extend. I suspect that the heart of your confusion actually has nothing to do with generators. -- Alan Bawden