Il 23 gennaio 2012 20:12, Erik Max Francis <m...@alcyone.com> ha scritto: > Giampaolo Rodolà wrote: >> >> Il 21 gennaio 2012 22:13, Erik Max Francis <m...@alcyone.com> ha scritto: >>> >>> The real reason people still use the `while 1` construct, I would >>> imagine, >>> >>> is just inertia or habit, rather than a conscious, defensive decision. >>> If >>> it's the latter, it's a case of being _way_ too defensive. >> >> >> It's also because while 1 is faster: > > ... >> >> while True: 1.41121292114 >> while 1: 1.07101011276 >> >> Most of the times tha't won't make any noticeable difference, but it's >> also true that certain while loops are going to iterate milions of >> times. >> Think about receiving a 10 GB file by using a socket. You'd tipically >> have something like this: >> >> while 1: >> chunk = sock.recv(1024): >> if not chunk: >> break >> ... >> >> Now, that's a case where I (personally) want to explicitly use "while >> >> 1" instead of "while True". > > > Such a loop would obviously be I/O-bound, not CPU-bound. So changing the > form of the while loop would make minimal difference to its overall > performance. It'd be spending the vast majority of its time blocked at the > OS socket level, not executing the condition of the while loop. > > As with most of these things, if one is this worried about performance, then > either Python was the wrong choice to begin with, or there's a good chance > that you're worried about something that isn't actually where the bottleneck > is in the first place. > > > -- > Erik Max Francis && m...@alcyone.com && http://www.alcyone.com/max/ > San Jose, CA, USA && 37 18 N 121 57 W && AIM/Y!M/Jabber erikmaxfrancis > Think twice before you speak to a friend in need. > -- Ambrose Bierce > -- > http://mail.python.org/mailman/listinfo/python-list
Obviously, you're right. I picked up the wrong example. My point is 1.41121292114 vs 1.07101011276 *might* make some difference in certain cases. I just can't come up with a good example where that would be justified. =) --- Giampaolo http://code.google.com/p/pyftpdlib/ http://code.google.com/p/psutil/ http://code.google.com/p/pysendfile/ -- http://mail.python.org/mailman/listinfo/python-list
