Generators/iterators, Pythonicity, and primes

Duncan Booth duncan.booth at invalid.invalid
Sun Apr 12 14:27:25 CEST 2009

John Posner <jjposner at> 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.

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