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Re: round down to nearest number

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On 10 February 2012 06:21, Ian Kelly <ian.g.kelly@gmail.com> wrote:
>>>>> (3219 + 99) // 100 * 100
>> 3300
>>>>> (3289 + 99) // 100 * 100
>> 3300
>>>>> (328678 + 99) // 100 * 100
>> 328700
>>>>> (328 + 99) // 100 * 100
>> 400
>>
>> Those are all rounded up to the nearest 100 correctly.
>
> One thing to be aware of though is that while the "round down" formula
> works interchangeably for ints and floats, the "round up" formula does
> not.
>
>>>> (3300.5 + 99) // 100 * 100
> 3300.0
>

I'm surprised I haven't seen:

>>> 212 - (212 % -100)
300

Here's a function that:
* rounds up and down
* works for both integers and floats
* is only two operations (as opposed to 3 in the solutions given above)

>>> def round(n, k):
...     return n - n%k
...
>>> # Round down with a positive k:
... round(167, 100)
100
>>> round(-233, 100
... )
-300
>>> # Round up with a negative k:
... round(167, -100)
200
>>> round(-233, -100)
-200
>>> # Edge cases
... round(500, -100)
500
>>> round(500, 100)
500
>>> # Floats
... round(100.5, -100)
200.0
>>> round(199.5, 100)
100.0

-- 
Arnaud

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round down to nearest number noydb <jenn.duerr@gmail.com> - 2012-02-09 16:30 -0800
  Re: round down to nearest number Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-09 17:47 -0700
    Re: round down to nearest number noydb <jenn.duerr@gmail.com> - 2012-02-09 17:23 -0800
      Re: round down to nearest number Chris Rebert <clp2@rebertia.com> - 2012-02-09 17:43 -0800
        Re: round down to nearest number Olive <diolu@bigfoot.com> - 2012-02-10 21:56 +0100
      Re: round down to nearest number Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-09 19:00 -0700
        Re: round down to nearest number noydb <jenn.duerr@gmail.com> - 2012-02-09 18:25 -0800
          Re: round down to nearest number MRAB <python@mrabarnett.plus.com> - 2012-02-10 03:36 +0000
          Re: round down to nearest number Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-09 23:21 -0700
          Re: round down to nearest number Arnaud Delobelle <arnodel@gmail.com> - 2012-02-10 09:58 +0000
            Re: round down to nearest number noydb <jenn.duerr@gmail.com> - 2012-02-10 09:23 -0800
          Re: round down to nearest number Alec Taylor <alec.taylor6@gmail.com> - 2012-02-10 22:05 +1100
      Re: round down to nearest number Terry Reedy <tjreedy@udel.edu> - 2012-02-09 22:29 -0500
        Re: round down to nearest number Hrvoje Niksic <hniksic@xemacs.org> - 2012-02-11 11:26 +0100
      Re: round down to nearest number MRAB <python@mrabarnett.plus.com> - 2012-02-10 03:39 +0000

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