[Numpy-discussion] casting

Hans Meine meine@informatik.uni-hamburg...
Wed Jan 16 10:27:21 CST 2008

Am Montag, 14. Januar 2008 19:59:15 schrieb Neal Becker:
> I don't want to use FROM_O here, because I really can only handle certain
> types.  If I used FROM_O, then after calling FROM_O, if the type was not
> one I could handle, I'd have to call FromAny and convert it.
What is the problem with that?  Is there any, apart from the code not being as 
elegant as one might want it to be?

AFAICS, it would be nice to have a function that takes a PyObject and a list 
of supported types and would perform the minimal needed conversion.  OTOH, if 
your code is templatized, it is maybe already written in an STL-style way, 
using iterators?  Then, it would be very simple to provide a set of iterators 
that e.g. promote unsigned short->int such that your algorithm can work on 
the original data without creating a copy.

Note that internally, ufuncs already do what you want.  I have not yet found 
the perfect way for a NumPy/C++ integration (which I am interested in, 
possibly using boost::python which I have been doing for the last years), but 
for element-wise operators, it would be very cool to be able to re-use the 
ufunc mechanism (i.e. only implement the inner loop, not caring about 
non-contiguous arrays etc.).

Ciao, /  /
    /  / ANS

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