Re: Issues accessing class attributes of external package distance function

> > I just committed some changes to pww3 that allow you to access or call
> > non-public Java fields/methods
>
> Setting accessible would allow this I think. A simple subclass changing the protected access still seems easier to me in this case. It’s also a legitimate java way to do this without bypassing or modifying the access of the class.

I didn't want to bog this thread down with specifics...

pww3 communicates with a JVM in the background that holds the Weka
classes/processes. It uses the python-javabridge library under the
hood and a lot of ugly-looking calls via method signatures behind the
scenes to make it look nice/pythonic (signatures are obtained via
"javap -public -s ..."). Some additional helper methods (on the Java
side of pww3 and with Python wrappers again) set the accessible flag,
to make these non-public fields/methods available.

[...]

> Possibly this makes it easier from Python if the intention is really to have little or nothing to do with the java.

That's the point. The idea is not to have to add additional Java
classes to get around these access issues. Especially, when people are
not familiar with Java and how to create Weka packages.

> If the intention isn’t to include this in a Weka java based package I’m still unclear on how it is meant to be provided. Again possibly I don’t understand well enough how the Python works.

Not quite sure what you mean. The DilcaDistance class (which is
already available as a Weka package) has a protected field. OP wants
to access this field directly and turn the stored matrices into numpy
arrays with no precision loss which currently happens when parsing the
toString() output of said class.

Accessing non-public members/methods is not a very common use-case,
but sometimes required when you need internally computed/held data
structures for further processing.
Over the years, I've had to sub-class plenty of classes to get access
to such data structures. Annoying, but not really a biggie when you're
already programming in Java.

Cheers, Peter
-- 
Peter Reutemann
Dept. of Computer Science
University of Waikato, NZ
+64 (7) 858-5174 (office)
+64 (7) 577-5304 (home office)
https://www.cs.waikato.ac.nz/~fracpete/
http://www.data-mining.co.nz/
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