[Python] How to return an array in ctypes when calling a function

What I want to do is to convert a C function into python function.

For example, I have a C function prototype which is pre-defined:

function_test(ViInt32 Arraysize, ViReal64 readingArray[], ViInt32 *Actual_rraysize)


The input of the above function is Arraysize, which is the number of elements in the readingArray parameter.

The outputs of the above function are readingArray[] and Arraysize. readingArray[] returns an array of the result and Actual_arraysize indicates the actual size of the returned array.

And the following is the Python function I wrote by using this C function prototype:

from ctypes import *
def Py_function_test(self, arraysize, readingarray = [], actualarraysize = [-1e-10]):
while len(readingarray) < arraysize:
readingarray.append(0)
_c_actualarraysize = c_int()
ArrayOfDouble = c_double * arraysize
_c_readingarray = ArrayOfDouble()
self.function_test(c_int(arraysize),
byref(_c_readingarray),
byref(_actualarraysize))
for n in range(arraysize):
readingarray[n] = _c_readingarray[n]
actualarraysize[0] = _c_actualarraysize.value


In the end, it turned out the value of acutalarraysize is successfully changed. But the value of readingarray didn't change after calling the c function prototype.

How to deal with this situation, is it because I should not have used the byref?

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