The Numpy version of modulo uses a different sign convention for negative arguments than does Python itself:
-5 % 3
1
array((-5,-5)) % 3
array([-2, -2])
(Numpy version 20.2.0, Python version 1.5.2 and version 2.2a4.)
Is there a reason for this (hard to imagine), or is this a bug?
Eric
On Fri, 12 Oct 2001, Eric Nodwell wrote:
The Numpy version of modulo uses a different sign convention for negative arguments than does Python itself:
...
Is there a reason for this (hard to imagine), or is this a bug?
Numpy delegates to the C platform's / and % operators, Python does it "right".
Maybe this should go on the FAQ.
Waren Focke
On Fri, 12 Oct 2001, Eric Nodwell wrote:
Numpy delegates to the C platform's / and % operators, Python does it "right".
Wouldn't it be preferable to change Numpy so it is also "right"?
Speed. In Python, there's so much overhead from symbol resolution, looking up __mod__s and __rmod__s and whatnot that the extra work is lost in the noise. Numpy would take a bigger hit when working with large arrays. One could always write python_compatible_div and python_compatible_mod functions, if one wanted. Could even submit a patch to add them, if truly motivated.
Warren Focke
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Eric Nodwell -
Warren Focke