Hallo!
As chris said, I need to make an example:
http://grh.mur.at/software/numpy2carray.tar.gz
I added the following class-example:
class_example.h: the C++ code
class_example.i: the SWIG interface file
class_example_usage.py: example usage in python
And some comments:
Bill Spotz schrieb:
> Here is what I am proposing you do: in your interface file, add
> something like
>
> PyObject * getMatrix()
> {
> npy_intp dims[2] = { /* Obtain the dimensions to your internal
> matrix */ };
> double * data = /* Obtain the pointer to you internal matrix */;
> return PyArray_SimpleNewFromData(2, dims, NPY_DOUBLE, (void*)data);
> }
>
> For your function, use the INPLACE_ARRAY2 typemap:
>
> %apply (double* INPLACE_ARRAY2, int DIM1, int DIM2) {(double*
> matrix, int rows, int cols)};
> void myFunction(double* matrix, int rows, int cols, double
> parameter, ...);
>
> And then in python you can do this:
>
> m = getMatrix()
> myFunction(m, 3.14, ...)
I see ... but what I mean with output of a matrix without copy is
actually only your getMatrix() funtion I guess - this is basically what
getBigData() does in class_example.h together with class_example.i.
BTW: what is the difference between PyArray_SimpleNewFromData() and
PyArray_FromDimsAndData() ?
(I don't have this book ...)
>> Again I do not see the problem - see e.g. ARRAY2_OUT_COPY in
>> numpy2carray.i, shouldn't this be the same ?
>
> I do not understand the use case for which that typemap works. You
> create "ttype t1", then pass its address to the function as the pointer
> to the data. This has to be useless to the function. After the
> function returns, you access this pointer as if it points to meaningful
> data. How is this possible? The address of t1 isn't going to change,
> and only a single element is allocated.
See also the class_example_usage.py - there I used the ARRAY2_OUT_COPY
for the getBigDataCopy() method.
LG
Georg
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