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classification
Title: Modulus not returning proper remainder
Type: behavior Stage: resolved
Components: Versions: Python 3.4
process
Status: closed Resolution: not a bug
Dependencies: Superseder:
Assigned To: Nosy List: DenisCrnic, r.david.murray
Priority: normal Keywords:

Created on 2014-09-04 21:40 by DenisCrnic, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Files
File name Uploaded Description Edit
Screenshot_1.png DenisCrnic, 2014-09-04 21:40 I'm attaching file in which it shows how modulus should work. that's how it works in Java.
Messages (2)
msg226381 - (view) Author: (DenisCrnic) Date: 2014-09-04 21:40
Modulus is returning wrong remainder when working with negative numbers.
For example 34%-3 should return 1, but it returns -2.

34/-3=-11, remainder: 1, proof: -11*(-3)+1=34 <--- Math logic (works in Java for example)

but python goes like that:
34/-3=12, remainder: -2. proof: -12*(-3)+(-2)=34 <--- Python logic (works)
I know that python is looking for the int which is the closest to the a (a%b), and is divisible with it, but in this case that's not right. it should seek for the closest integer, which is lower than a, in this case 33

If explanation is not clear enough, reply me, i'll take more time to make it clear.
maybe my theory is wrong, and python syntax works better than in Java.
msg226383 - (view) Author: R. David Murray (r.david.murray) * (Python committer) Date: 2014-09-04 22:01
This is, indeed, the way Python works.  See

https://docs.python.org/3/reference/expressions.html

where you will find:

The modulo operator always yields a result with the same sign as its second operand (or zero); the absolute value of the result is strictly smaller than the absolute value of the second operand
History
Date User Action Args
2022-04-11 14:58:07adminsetgithub: 66533
2014-09-04 22:01:31r.david.murraysetstatus: open -> closed

nosy: + r.david.murray
messages: + msg226383

resolution: not a bug
stage: resolved
2014-09-04 21:40:20DenisCrniccreate