John Posner wrote:
Inspired by recent threads (and recalling my first message to Python edu-sig), I did some Internet searching on producing prime numbers using Python generators. Most algorithms I found don't go for the infinite, contenting themselves with "list all the primes below a given number".Here's a very Pythonic (IMHO) implementation that keeps going and going and going ...: from itertools import count from math import sqrt def prime_gen(): """ Generate all prime numbers """ primes = [] for n in count(2): if all(n%p for p in primes if p < sqrt(n)): primes.append(n) yield n The use of all() is particularly nifty (see http://code.activestate.com/recipes/576640/). And so is the way in which the list comprehension easily incorporates the sqrt(n) optimization. Question: Is there a way to implement this algorithm using generator expressions only -- no "yield" statements allowed?
No. You refer to the list being build in the code for building the list (very cute), which requires that the list be bound to a name at the start of the process rather than just when complete (which is never ;-).
tjr -- http://mail.python.org/mailman/listinfo/python-list
