Sieve Of Eratosthenes

sieve.py

#!/usr/bin/env python

################################################
# Sieve Of Eratosthenes
# Implementation the sieve of eratosthenes for
# finding all prime numbers up to a given limit
# Author: Samuel Jackson (slj11@aber.ac.uk)
# Date: 4/8/13
################################################

import math

def sofe(n):
  #list of flags from 2 to n indidcating if a number is prime
  lstFlags = [True]*n

  #for each number between 2 and the largest possible divisor of the limit
  for i in range(2, 1+int(math.sqrt(n))):
    #check if the current number is prime
    if(lstFlags[i] is True):
      #if so, remove any multiples of i from the pool
      for j in range(i**2, n, i):
        lstFlags[j] = False

  #filter the list of flags to return only the primes.
  return [i for i, x in enumerate(lstFlags) if x is True and i > 1]

if __name__ == "__main__":
  number = raw_input("Input a number: ")

  try:
    number  = int(number)
  except exceptions.ValueError:
    print "That wasn't a number!"

  print sofe(number)