Re: [Tutor] primes

[Max Noel]

On Mar 17, 2005, at 22:28, Gregor Lingl wrote:
Hi!
Who knows a more concise or equally concise but more efficient
expression, which returns the same result as
[x for x in range(2,100) if not [y for y in range(2,x) if x%y==0]]
Gregor
P.S.: ... or a more beautiful one ;-)
	Hmm... I don't have "beautiful" or "concise", but I can offer "fast". 
Here goes:

#!/usr/bin/env python
import math
def isPrime(x, primeList):
    limit = math.sqrt(x)
    for i in primeList:
        if x % i == 0:
            return False
        if i >= limit:
            break
    return True
def listPrimes(upperLimit):
    listOfPrimes = []
    for i in range(2, upperLimit):
        if isPrime(i, listOfPrimes):
            listOfPrimes.append(i)
    return listOfPrimes
if __name__ == '__main__':
    import sys
    num = int(sys.argv[-1])
    print listPrimes(num)

	That's the fastest way I can think of -- but I can't prove it, as I 
don't know how to use the timeit module.

-- Max
maxnoel_fr at yahoo dot fr -- ICQ #85274019
"Look at you hacker... A pathetic creature of meat and bone, panting 
and sweating as you run through my corridors... How can you challenge a 
perfect, immortal machine?"

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