[David Mertz]

Oops... yeah. I had fixed the "up to and including" previously, but somehow I copied the wrong version to the thread.

Doesn't matter ;-) The point here, to me, is that the prime generator I pointed at is significantly faster, more memory-frugal, and even "more correct", than even experienced Python programmers are likely to come up with at first. That gives it real value as a candidate for a standard library. But something much fancier than that? I don't think so, for reasons already given - the code is still understandable for non-experts if they give it some effort. Fancier stuff may not be. For example, in my own code I use a fancier version of that incorporating a wheel sieve too, and even the _setup_ function for that is harder to understand all on its own: def _setup_sieve(ps, show=True): from math import gcd assert ps[0] == 2 prod = totient = 1 for p in ps: assert pp(p) prod *= p totient *= p-1 if show: print("ps", ps, "prod", prod) mod2i = [None] * prod mod2i[1] = 0 deltas = [] last = 1 for i in range(3, prod, 2): if gcd(prod, i) == 1: deltas.append(i - last) mod2i[i] = len(deltas) last = i deltas.append(2) # wrap around from prod-1 to 1 assert len(deltas) == totient assert sum(deltas) == prod if show: print("deltas", deltas, len(deltas)) print("mod2i", mod2i) return ps, deltas * 2, mod2i _siv_glob = _setup_sieve([2, 3, 5, 7], show=False) I don't want that in the standard library - and twice as much don't want it if somebody else wrote it ;-)