def rwh_primes1(n):
    # http://stackoverflow.com/questions/2068372/fastest-way-to-list-all-primes-below-n-in-python/3035188#3035188
    ''' Returns  a list of primes < n '''
    sieve = [True] * (n/2)
    for i in xrange(3,int(n**0.5)+1,2):
        if sieve[i/2]:
            sieve[i*i/2::i] = [False] * ((n-i*i-1)/(2*i)+1)
    return [2] + [2*i+1 for i in xrange(1,n/2) if sieve[i]]
def rwh_primes1 ( n ) : sieve = [ True ] * ( n / 2 ) for i in xrange ( 3 , int ( n ** 0.5 ) + 1 , 2 ) : if sieve [ i / 2 ] : sieve [ i * i / 2 : : i ] = [ False ] * ( ( n - i * i - 1 ) / ( 2 * i ) + 1 ) return [ 2 ] + [ 2 * i + 1 for i in xrange ( 1 , n / 2 ) if sieve [ i ] ]
Returns  a list of primes < n