Safer way to expose a C-allocated memory buffer using numpy/ctypes?

You have to keep a reference to your Wrapper while any numpy array exists. Easiest way to achieve this, is to save this reference in a attribute of the ctype-buffer:

class MyWrapper(object):
    def __init__(self, n=10):
        # buffer allocated by external library
        self.size = n
        self.addr = libc.malloc(C.sizeof(C.c_int) * n)

    def __del__(self):
        # buffer freed by external library
        libc.free(self.addr)

    @property
    def buffer(self):
        buf = (C.c_int * self.size).from_address(self.addr)
        buf._wrapper = self
        return np.ctypeslib.as_array(buf)

This way you’re wrapper is automatically freed, when the last reference, e.g the last numpy array, is garbage collected.