[Numpy-discussion] Faster way to generate a rotation matrix?

Robert Kern robert.kern@gmail....
Wed Mar 4 00:58:54 CST 2009


On Wed, Mar 4, 2009 at 00:56, David Warde-Farley <dwf@cs.toronto.edu> wrote:
> On 3-Mar-09, at 11:41 PM, Jonathan Taylor wrote:
>
>> def rotation(theta, R = np.zeros((3,3))):
>
> Hey Jon,
>
> Just a note, in case you haven't heard this schpiel before: be careful
> when you use mutables as default arguments. It can lead to unexpected
> behaviour down the line.
>
> The reason is that the np.zeros() is only called once when the
> function is read by the interpreter, and that reference is retained
> between calls.

I'm pretty sure that's exactly why he did it, and that's what he's calling evil.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco


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