We've maybe seen this sieve before on edu-sig but I don't remember for sure, and just came across it following links from Guido's blog. So pithy! # -*- coding: utf-8 -*- """ Created on Thu Nov 16 13:23:51 2017 Copied from: http://www.mypy-lang.org/examples.html """ import itertools def iter_primes(): # An iterator of all numbers between 2 and # +infinity numbers = itertools.count(2) # Generate primes forever while True: # Get the first number from the iterator # (always a prime) prime = next(numbers) yield prime # This code iteratively builds up a chain # of filters... numbers = filter(prime.__rmod__, numbers) for p in iter_primes(): if p > 1000: break print(p) ------- Also, anyone interested in debates regarding the future of high school math might be interested in math-teach, likely to be frozen and/or disappeared come first of next year. Lots of politics (I'm not a listowner nor on staff, have limited insight, see 2nd link below): http://mathforum.org/kb/message.jspa?messageID=10283328 https://www.nctm.org/News-and-Calendar/Messages-from-the-President/Archive/M... Kirby