Getting data from ctypes array into numpy

Question

I am using a Python (via ctypes) wrapped C library to run a series of computation. At different stages of the running, I want to get data into Python, and spec

Answer 1

Neither of these worked for me in Python 3. As a general solution for converting a ctypes pointer into a numpy ndarray in python 2 and 3 I found this worked (via getting a read-only buffer):

def make_nd_array(c_pointer, shape, dtype=np.float64, order='C', own_data=True):
    arr_size = np.prod(shape[:]) * np.dtype(dtype).itemsize 
    if sys.version_info.major >= 3:
        buf_from_mem = ctypes.pythonapi.PyMemoryView_FromMemory
        buf_from_mem.restype = ctypes.py_object
        buf_from_mem.argtypes = (ctypes.c_void_p, ctypes.c_int, ctypes.c_int)
        buffer = buf_from_mem(c_pointer, arr_size, 0x100)
    else:
        buf_from_mem = ctypes.pythonapi.PyBuffer_FromMemory
        buf_from_mem.restype = ctypes.py_object
        buffer = buf_from_mem(c_pointer, arr_size)
    arr = np.ndarray(tuple(shape[:]), dtype, buffer, order=order)
    if own_data and not arr.flags.owndata:
        return arr.copy()
    else:
        return arr