[Python-Dev] Return type of round, floor, and ceil in 2.6
Guido van Rossum
guido at python.org
Fri Jan 4 18:05:43 CET 2008
On Jan 4, 2008 8:58 AM, <skip at pobox.com> wrote:
> Guido> Looks like in Python 2.6, round(0.5) right now returns 0.0,
> Guido> whereas in 2.5, it returns 1.0.
> Guido> I think it should return 1.0, for best compatibility with Python
> Guido> 2.5.
> And for best compatibility with everything else! <0.5 wink>
Should I round that to 0 whole winks or 1 whole wink?
Rounding 0.5 to 0 is a new fad, called round-to-even, or
statistician's rounding. Read http://en.wikipedia.org/wiki/Rounding .
It's a standard, and more correct when doing statistical calculations.
That's why we've chosen it for Python 3.0. But it should not bleed
into Python 2.6.
--Guido van Rossum (home page: http://www.python.org/~guido/)
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