[SciPy-user] sequence emulation -/-> array access?
jdc at uwo.ca
Sat Dec 17 21:14:20 CST 2005
Travis Oliphant <oliphant.travis at ieee.org> writes:
> So, you should be able to subclass rather easily.
Great, glad to hear it!
> The only confusion,
> perhaps, is that the array function *is not* a __new__ method. The
> ndarray.__new__ method has arguments that are slightly different. There
> are basically two ways to create an array (as an empty array or from a
> buffer). The docstring of ndarray has more information in newer
> versions: help(ndarray). Also, look at matrix.py, chararray.py,
> records.py, and memmap.py for examples of how to subclass.
> Basically, you need to define the __new__ method (the only thing that's
> necessary, no __init__ is needed). Then define __mul__ and __add__ the
> way you want.
> from scipy import ndarray
> class mysub(ndarray):
> def __new__(self, *args):
> #you need to call ndarray.__new__ in here with one of two sets
> of arguments
I guess what you are saying is that it's not generally useful to
create an array directly with
arr = ndarray(...params...)
and so if I subclass without overriding the __new__ method, I won't
be able to conveniently create objects of my new class with
myob = mysub(...param...)
I'm a bit confused by why ndarray is designed in a way that makes this
necessary, but I should be able to imitate what is done in matrix.py,
etc, to do what I want. I haven't yet installed scipy core but will
hopefully find time to play with it soon.
Thanks so much for the detailed help!
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