[Tutor] primes

[C Smith]

On Thursday, Mar 17, 2005, at 17:49 America/Chicago, 
tutor-request at python.org wrote:

> On my system, it took 415 seconds to generate a list of primes < 50,000
> using range, but only 386 seconds if I use the same code, but with 
> xrange instead.
>
>
If you only calculate y up to sqrt(x) you will see a dramatic time 
reduction:

###
import math
big=50000
[x for x in xrange(2,big) if not [y for y in 
range(2,int(math.sqrt(x)+1)) if x%y==0]]
###

/c