On May 30, 4:10 pm, Steven D'Aprano <st...@remove-this- cybersource.com.au> wrote: > On Sat, 30 May 2009 12:06:55 +0200, jkv wrote: > > I added a few lines to your script, and now it ought to only print files > > newer than 3601 seconds (3600 seconds is one hour). > ... > > #if file newer than one hour print a line > > if time_difference < 3601: > > That's a potential off-by-one error. That may print files that are older > than one hour. Admittedly, they'll be off by less than one second, but if > you're going to write code, write correct code. The right test is: > > if time_difference <= 3600: > > (and you may even want to deal with files that have a *negative* time > difference, e.g. they were created apparently in the future). > > This is particularly necessary if you use time.time() to generate the > current time, since that returns fractions of a second. But even if you > don't, it's still the right thing to do: it's defensive programming. > Rather than assume that all file systems store timestamps accurate only > to a second, assume that some file system, somewhere, will be accurate to > fractions of a second, and code accordingly. > > That way, no matter what the file system does, your code will still do > the right thing, and (in this case) it doesn't even cost you anything. > > -- > Steven
Hi Steve thanks for your comment. But I only need it to re-run some test scripts in case there seems to be hick-up in our live download of satellite images. It's not critical within seconds, not even within minutes... But in principel the potential error could of cause be important - in other context. :-) M -- http://mail.python.org/mailman/listinfo/python-list
