[Numpy-discussion] access ndarray in C++

Joris De Ridder Joris.DeRidder@ster.kuleuven...
Tue Apr 22 20:56:21 CDT 2008


On http://www.scipy.org/JorisDeRidder I've just put an example how I  
passed multidimensional Numpy arrays to C++ using ctypes. Perhaps it's  
helpful for your application. I didn't put it in the cookbook yet,  
because I would first like to test it a bit more. Up to now I didn't  
experience any bugs though.

Joris



On 22 Apr 2008, at 23:38, Thomas Hrabe wrote:

> Hi all!
>
> I am currently developing a python module in C/C++ which is supposed  
> to access nd arrays as defined by the following command in python
>
> a = numpy.array([1,1,1])
>
> I want to access the array the following way and use the nd array  
> data for further processing in C.
>
> mymod.doSthg(a)
>
> The example code on
> http://numpy.sourceforge.net/numdoc/HTML/numdoc.htm#pgfId-36721
>
>  (!PyArg_ParseTuple(args, "O!",&PyArray_Type, &array))
>
> does not work for nd arrays. I always get
> TypeError: argument 1 must be array, not numpy.ndarray
>
> I assume the error is the constant provided as the third parameter,  
> saying that the imput is of PyArray_Type and no nd array.
>
> So here are my questions:
> 1. is there any good tutorial / example code for acessing nd arrays  
> in C?
> 2. what is the difference between both (arrays and nd arrays? - I am  
> new to python and heard there were different approaches to arrays  
> and that nd arrays work better for multi dimensional applications.  
> Is this right?)
> 3. which one of both will be used in the future?
>
> Thank you in advance for your help,
> Thomas
>
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