[Numpy-discussion] [C++-sig] Overloading sqrt(5.5)*myvector
Bruce Sherwood
Bruce_Sherwood@ncsu....
Wed Dec 26 22:35:16 CST 2007
Thanks for the suggestion. It hadn't occurred to me to try to override
numpy as you suggest. However, when I try the code shown below as the
start of a test of this scheme, I get the following error:
Traceback (most recent call last):
File "C:\Documents and Settings\Bruce\My
Documents\0VPythonWork\vectors.py", line 24, in <module>
numpy.float64.__mul__ = new_mul
TypeError: can't set attributes of built-in/extension type 'numpy.float64'
I'm copying this to the numpy discussion list, as maybe someone there
will see where to go starting from your suggestion.
Bruce Sherwood
---------------
import numpy
class vector(object):
def __init__(self,x,y,z):
self.data = [x,y,z]
def __mul__(self,other):
return vector(other*self.data[0],
other*self.data[1],
other*self.data[2])
__rmul__ = __mul__
def show(self):
print self.data
old_mul = numpy.float64.__mul__
def new_mul( self, other ):
if isinstance( other, vector ):
return other*self
else:
return old_mul( self, other )
numpy.float64.__mul__ = new_mul
a = vector(1,2,3)
a.show()
b = 5*a
b.show()
c = a*7
c.show()
Roman Yakovenko wrote:
> On Dec 26, 2007 8:11 AM, Bruce Sherwood <Bruce_Sherwood@ncsu.edu> wrote:
>
>> Sorry to repeat myself and be insistent, but could someone please at
>> least comment on whether I'm doing anything obviously wrong, even if you
>> don't immediately have a solution to my serious problem? There was no
>> response to my question (see copy below) which I sent to both the numpy
>> and Boost mailing lists.
>>
>> To the Boost experts: Is there something wrong, or something I
>> could/should change in how I'm trying to define to Boost the overloaded
>> multiplication of a numpy square root (or other numpy function) times my
>> own "vector" object? I'm seeing a huge performance hit in going from
>> Numeric to numpy because Numeric sqrt returned float whereas numpy sqrt
>> returns numpy.float64, so that the result is not one of my vector
>> objects. I don't have a problem with myvector*sqrt(5.5). Here is what I
>> currently am doing:
>>
>> py::class_<vector>("vector", py::init< py::optional<double, double,
>> double> >())
>> .def( self * double())
>> .def( double() * self)
>>
>> Desperately,
>>
>
> If I understand you right, than you can do something like this:
>
> replace __mul__ method of numpy.float64 class:
>
> old_mul = numpy.float64.__mul__
>
> def new_mul( self, other ):
> if other isinstance( vector ):
> return other*self
> else:
> return old_mul( self, other )
>
> numpy.float64.__mul__ = new_mul
>
> HTH
>
>
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