On Sat, 18 Aug 2012 17:17:14 -0400 Terry Reedy <tjre...@udel.edu> wrote: > The issue came up in python-list about string operations being slower in > 3.3. (The categorical claim is false as some things are actually > faster.) Some things I understand, this one I do not. > > Win7-64, 3.3.0b2 versus 3.2.3 > print(timeit("c in a", "c = '…'; a = 'a'*1000+c")) # ord(c) = 8230 > # .6 in 3.2, 1.2 in 3.3
I get opposite numbers: $ python3.2 -m timeit -s "c = '…'; a = 'a'*1000+c" "c in a" 1000000 loops, best of 3: 0.599 usec per loop $ python3.3 -m timeit -s "c = '…'; a = 'a'*1000+c" "c in a" 10000000 loops, best of 3: 0.119 usec per loop However, in both cases the operation is blindingly fast (less than 1µs), which should make it pretty much a non-issue. > Why is searching for a two-byte char in a two-bytes per char string so > much faster in 3.2? Is this worth a tracker issue (I searched and could > not find one) or is there a known and un-fixable cause? I don't think it's worth a tracker issue. First, because as said above it's practically a non-issue. Second, given the nature and depth of changes brought by the switch to the PEP 393 implementation, an individual micro-benchmark like this is not very useful; you'd need to make a more extensive analysis of string performance (as a hint, we have the stringbench benchmark in the Tools directory). > This is one of the 3.3 improvements. But since the results are equal: > ('a'*1000).encode() == ('a'*1000).encode(encoding='utf-8') > and 3.3 should know that for an all-ascii string, I do not see why > adding the parameter should double the the time. Another issue or known > and un-fixable? When observing performance differences, you should ask yourself whether they matter at all or not. Regards Antoine. -- Software development and contracting: http://pro.pitrou.net _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com