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Numeric and the new division operator

Chris Liechti cliechti at gmx.net
Thu Jan 3 10:19:43 EST 2002 
[posted and mailed]

mjbarber at ascc.artsci.wustl.edu (Michael James Barber) wrote in
news:a11rau$h3h at ascc.artsci.wustl.edu: 

> 
> I run into a problem when using the new "true division" operator in 
> conjunction with Numeric.  Do others see this too?
> 
> I can't imagine what I could be doing wrong with what is below, but I
> hope someone can enlighten me if it is a usage problem.  The problem is
> only in Numeric, btw - it works fine with floats and integers.
> 
> 
> Python 2.2 (#124, Dec 22 2001, 17:36:41)  [CW CARBON GUSI2 THREADS GC]
> on mac
> Type "copyright", "credits" or "license" for more information.
>>>> from Numeric import arange
>>>> x = arange(10)
>>>> x
> array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>>> x / 10
> array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0])
>>>> x / 10.
> array([ 0. ,  0.1,  0.2,  0.3,  0.4,  0.5,  0.6,  0.7,  0.8,  0.9])
>>>> # classic division works as expected ... 
>>>> # now let's try true division ... 
>>>> from __future__ import division x/10
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: unsupported operand type(s) for /: 'array' and 'int'
>>>> x / 10.
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: unsupported operand type(s) for /: 'array' and 'float'
>>>> # oh, dear

from the docs:
---------
__div__(self, other) 
__truediv__(self, other) 
The division operator (/) is implemented by these methods. The 
__truediv__() method is used when __future__.division is in effect, 
otherwise __div__() is used. If only one of these two methods is defined, 
the object will not support division in the alternate context; TypeError 
will be raised instead.
---------

so i think they have not implemented __truediv__.
maybe it would suffuce to say "__truediv__ = __div__" in the Nummeric 
classes, but i don't know them.


-- 
Chris <cliechti at gmx.net>
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