On Thu, May 7, 2015 at 7:14 PM, Alain Ketterlin <al...@universite-de-strasbourg.fr.invalid> wrote: > Dave Angel <da...@davea.name> writes: > >> On 05/06/2015 11:36 AM, Alain Ketterlin wrote: >>> Yes, plus the time for memory allocation. Since the code uses "r *= >>> ...", space is reallocated when the result doesn't fit. The new size is >>> probably proportional to the current (insufficient) size. This means >>> that overall, you'll need fewer reallocations, because allocations are >>> made in bigger chunks. >> >> That sounds plausible, but a=5; a*=4 does not update in place. It >> calculates and creates a new object. Updating lists can work as you >> say, but an int is immutable. > > Ah, okay. Even for big ints? If that is the case, my suggestion doesn't > explain anything. Anyway, with so many allocations for so little > arithmetic, the difference is probably due to the behavior of the > allocator (which maybe always finds blocks big enough, since one was > released after the previous multiplication, or something like that). The > only way to know would be to profile the VM.
Yes, all integers are immutable. This is true regardless of the size of the integer, because: x = some_big_long_calculation() y = x y += 1 should never change the value of x. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
