[Numpy-discussion] Subclassing numarray arrays
jmiller at stsci.edu
Thu Sep 25 13:20:05 CDT 2003
On Thu, 2003-09-25 at 12:14, Colin J. Williams wrote:
> Thanks for the benchmark data.
Thanks for the references. They suggest that the classmethod approach
we've already tried for folding in the numarray factory functions is
> I intend to post the matrix stuff. Performance is not a problem for me
> at this stage.
> Currently, I'm plodding along, making things work. Later, I'll post it
> with some rudimentary documentation.
> Regarding the "new-classes standard", I can't find much in either the
> Python docs or Alex Martelli's "Python in a Nutshell". One of the new
> features is a __new__ constructor.
Well, we've certainly got those (__new__ methods). They don't match
the __init__ signature though, nor was I aware that they should.
> The Python array module doesn't formally have a class and thus it can't
> be sub-classed. It uses a factory function to create instance objects.
> Martelli, in PIAN p74, writes of factory functions being useful when one
> wishes to create instances of different classes depending on some
> condition or for the reuse of an existing instance.
> In the Python Cookbook p173, he proposes the use of a factory function
> to get around the limitations of Python 2.1 and earlier. On page 179,
> he refers to the use of a factory method, again to work around
> limitations before Python 2.2.
> My rough and ready definition would include the ability to create an
> instance and initialize
> the data in one step.
One thing to keep in mind is that NumArray was designed to run on
Python-2.0. As Python-2.2 became widely available and stable, we
realized we could exploit it for better C-API compatibility with
Numeric, and for better speed.
I think what you and later Nadav have pointed out is that we can exploit
Python-2.2 for better sub-classing as well. We just haven't done it
yet. Concrete proposals are welcome.
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