ctypes pointer into the middle of a numpy array

Question

I know how to get a ctypes pointer to the beginning of a numpy array:

a = np.arange(10000, dtype=np.double)
p = a.ctypes.data_as(POINTER(c_double))
p.contents
c_double(0.0)

however, I need to pass the pointer to, let's say, element 100, without copying the array. There must be an easy way to do it but cannot find it.

Any hint appreciated.

senderle · Accepted Answer · 2011-06-25 20:37:23Z

11

Slicing a numpy array creates a view, not a copy:

>>> a = numpy.arange(10000, dtype=numpy.double)
>>> p = a[100:].ctypes.data_as(ctypes.POINTER(ctypes.c_double))
>>> p.contents
c_double(100.0)
>>> a[100] = 55
>>> p.contents
c_double(55.0)

answered Jun 25, 2011 at 20:37

senderle

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