How to return array from C++ function to Python using ctypes

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Your python code will work after some minor modifications:

import ctypes

f = ctypes.CDLL('./library.so').function
f.restype = ctypes.POINTER(ctypes.c_int * 10)
print [i for i in f().contents] # output: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Basically there are two changes:

  1. remove numpy-related code and ctypes.cast call since we don’t need them.

  2. specify the return type to ctypes.POINTER(ctypes.c_int * 10).

    By default foreign functions are assumed to return the C int type, hence we need change it to the desired pointer type.

BTW, returning a newed array from C code to Python code seems inappropriate. Who and when will free the memory? It’s better to create arrays in Python code and pass them to C code. This way it’s clear that the Python code owns the arrays and takes the responsibility of creating and reclaiming their spaces.

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