[Numpy-discussion] numpy.ctypeslib.ndpointer and the restype attribute
Mon Mar 23 08:36:22 CDT 2009
So I have a C-function in a DLL loaded through ctypes. This particular
function returns a pointer to a double. In fact I know that this
pointer points to the first element in an array of, say for simplicity,
How do I convert this pointer to a NumPy array that uses this data (ie.
no copy of data in memory)? I am able to create a numpy array using a
copy of the data.
I have tried using the 'numpy.ctypeslib.ndpointer' but so far failed.
In its documentation it claims it should be possible to use for not
only argtypes attribute, but also restype. I have not found a single
example of this on the web, and I wonder how this is done. As I see it,
it would have to use the errcheck attribute to return an ndarray and
not just restype.
My latest trial was:
>>> import ctypes
>>> pointer = DLL.my_func()
>>> ctypes_arr_type = C.POINTER(200 * ctypes.c_double)
>>> ctypes_arr = ctypes_arr_type(pointer)
>>> narray = N.ctypeslib.as_array(ctypes_arr)
however this didn't work.
Any hints would be appreciated.
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