Joshua Bronson <jabron...@gmail.com> added the comment:
This was so surprising to me that I had to check some other languages that I had handy. It turns out that not one of JavaScript, Ruby, Perl, C++, Java, Go, or Rust agrees with Python. In fact they all agreed with one another that 2.5 should round to 3. Examples below. I understand from https://github.com/cosmologicon/pywat/pull/40#discussion_r219962259 that "to always round up... can theoretically skew the data" but it's not clear why that's a good enough reason to differ from the "round" function in all these other languages (as opposed to e.g. offering this alternative behavior in some additional "round_unskewed" function). I assume the rationale for having Python 3's "round" differ from that of so many other languages was written down when this decision was made, but I searched and couldn't find it. Could anyone link to it in a comment here? And would it be worth including rationale and a larger callout in the https://docs.python.org/3/library/functions.html#round docs? The documentation of this behavior is a bit buried among other things, and the rationale for it is missing entirely. $ node -e 'console.log(Math.round(2.5))' 3 $ ruby -e 'puts (2.5).round()' 3 $ perl -e 'use Math::Round; print round(2.5)' 3 $ cat test_round.cpp #include <stdio.h> #include <math.h> int main(void) { printf("%f\n", round(2.5)); } $ g++ test_round.cpp && ./a.out 3.000000 $ cat TestRound.java class TestRound { public static void main(String[] args) { System.out.println(Math.round(2.5)); } } $ javac TestRound.java && java TestRound 3 $ cat test_round.go package main import "fmt" import "math" func main() { fmt.Println(math.Round(2.5)) } $ go build test_round.go && ./test_round 3 $ cat test_round.rs fn main() { println!("{}", (2.5_f64).round()); } $ rustc test_round.rs && ./test_round 3 ---------- nosy: +jab _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue32956> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
