[Numpy-discussion] making the distinction between -0.0 and 0.0..

Gökhan Sever gokhansever@gmail....
Tue Sep 29 12:08:17 CDT 2009


On Tue, Sep 29, 2009 at 11:53 AM, Christopher Barker
<Chris.Barker@noaa.gov>wrote:

> Hi folks,
>
> This isn't really a numpy question, and I'm doing this with regular old
> python, but I figure you are the folks that would know this:
>
> How do I get python to make a distinction between -0.0 and 0.0? IN this
> case, I'm starting with user input, so:
>
> In [3]: float("-0.0")
> Out[3]: -0.0
>
> so python seems to preserve the "-". But:
>
> In [12]: float("-0.0") == float("0.0")
> Out[12]: True
>
> In [13]: float("-0.0") < float("0.0")
> Out[13]: False
>
> In [14]: float("0.0") > float("-0.0")
> Out[14]: False
>
> It doesn't seem to make the distinction between -0.0 and 0.0 in any of
> the comparisons. How can I identify -0.0?
>
> NOTE: numpy behaves the same way, which I think it should, but still...
>
> My back-up plan is to process the string first, looking for the minus
> sign, but that will require more changes than I'd like to the rest of my
> code...
>
> thanks,
> -Chris
>
>
>
> --
> Christopher Barker, Ph.D.
> Oceanographer
>
> Emergency Response Division
> NOAA/NOS/OR&R            (206) 526-6959   voice
> 7600 Sand Point Way NE   (206) 526-6329   fax
> Seattle, WA  98115       (206) 526-6317   main reception
>
> Chris.Barker@noaa.gov
> _______________________________________________
> NumPy-Discussion mailing list
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>

No help from the decimal module. Although its documentation (
http://docs.python.org/library/decimal.html) says:

*A decimal number is immutable. It has a sign, coefficient digits, and an
exponent. To preserve significance, the coefficient digits do not truncate
trailing zeros. Decimals also include special values such as Infinity,
-Infinity, and NaN. The standard also differentiates -0 from +0.*

When I try:

from decimal import *
a = Decimal('+0.0')
b = Decimal('-0.0')

a == b
True

No help for you either I guess :)

-- 
Gökhan
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