On Wed, 03 Sep 2008 16:20:39 -0700, Mensanator wrote: >>>> sum([]) > 0 > > is a bug, just as it's a bug in Excel to evaluate blank cells as 0. It > should return None or throw an exception like sum([None,1]) does.
You're wrong, because 99.9% of the time when users leave a blank cell in Excel, they want it to be treated as zero. Spreadsheet sum() is not the same as mathematician's sum, which doesn't have a concept of "blank cells". (But if it did, it would treat them as zero, since that's the only useful thing and mathematicians are just as much pragmatists as spreadsheet users.) The Excel code does the right thing, and your "pure" solution would do the unwanted and unexpected thing and is therefore buggy. Bugs are defined by "does the code do what the user wants it to do?", not "is it mathematically pure?". The current behaviour of sum([]) does the right thing for the 99% of the time when users expect an integer. And the rest of the time, they have to specify a starting value for the sum anyway, and so sum([], initial_value) does the right thing *always*. The only time it does the wrong thing[1] is when you forget to pass an initial value but expect a non-numeric result. And that's the programmer's error, not a function bug. [1] I believe it also does the wrong thing by refusing to sum strings, but that's another story. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
