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Created on 2022-01-22 02:36 by adam.ulrich, last changed 2022-04-11 14:59 by admin. This issue is now closed.
| Messages (3) | |||
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| msg411222 - (view) | Author: Adam Ulrich (adam.ulrich) | Date: 2022-01-22 02:36 | |
round(250,-2) returns 200 round(350,-2) returns 400 round(450,-2) returns 400 round(550,-2) returns 600 round(5,-1) returns 0 round(15,-1) returns 20 round(500,-3) returns 0 round(1500,-3) returns 2000 expected: round of 5 to consistently rounds up. |
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| msg411223 - (view) | Author: Spencer Brown (Spencer Brown) * | Date: 2022-01-22 02:58 | |
This is intentional behaviour, if the value is 5 it rounds towards even as documented here: https://docs.python.org/3/library/functions.html#round The reason is so that if you have a bunch of random data, rounding won't slightly bias the result upward or downward. |
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| msg411227 - (view) | Author: Steven D'Aprano (steven.daprano) *  |
Date: 2022-01-22 03:29 | |
As documented, this is not a bug. "if two multiples are equally close, rounding is done toward the even choice" https://docs.python.org/3/library/functions.html#round This is also called "Banker's Rounding" or "Round half to even" and for rounding many values, it minimizes the expected total rounding error. https://en.wikipedia.org/wiki/Rounding#Round_half_to_even |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:55 | admin | set | github: 90625 |
| 2022-01-22 03:29:09 | steven.daprano | set | status: open -> closed nosy: + steven.daprano messages: + msg411227 resolution: not a bug stage: resolved |
| 2022-01-22 02:58:28 | Spencer Brown | set | nosy:
+ Spencer Brown messages: + msg411223 |
| 2022-01-22 02:36:11 | adam.ulrich | create | |