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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Thu, 9 Feb 2012 23:21:31 -0700
Subject: Re: round down to nearest number
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:20142

On Thu, Feb 9, 2012 at 8:36 PM, MRAB <python@mrabarnett.plus.com> wrote:
> On 10/02/2012 02:25, noydb wrote:
>>
>> That {>>> =A0(3219 + 99) // 100} doesnt work if the number is other then
>> 4 digits.
>>
>>
>> (for rounding up to nearest 100):
>>>>>
>>>>> =A0(3219 + 99)//100
>>
>> 33
>>>>>
>>>>> =A0(3289 + 99)//100
>>
>> 33
>>>>>
>>>>> =A0(328678 + 99)//100
>>
>> 3287
>>>>>
>>>>> =A0(328 + 99)//100
>>
>> 4
>
>
>>>> (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

A more consistent alternative is to negate the number, round down, and
then negate again.

>>> -(-(3300.5) // 100 * 100)
3400.0

Cheers,
Ian