Generators/iterators, Pythonicity, and primes

[Duncan Booth]

John Posner <jjposner at snet.net> wrote:

> Do know what in the itertools implementation causes adding a 'if p <=
> sqrt(n)' clause to *decrease* performance, while adding a
> 'takewhile()' clause *increases* performance? 

I haven't timed it, but I would guess that the takewhile was faster 
only because the sqrt(n) had been factored out of the loop. Try the 
original loop again precalculating the sqrt(n) and see how that compares.