test = cdll('mydll')
test.Operation.restype = c_bool
test.Operation.argtypes = [POINTER(c_void_p)]
test.GetFieldValue.restype = c_float
test.GetFieldValue.argtypes = [c_void_p]
test.Cleanup.restype = None
test.Cleanup.argtypes = [c_void_p]
if __name__ == '__main__':
    p = c_void_p()
if test.Operation(byref(p)):
    theAnswer = test.GetFieldValue(p)
test.Cleanup(p)
C на Python через SWIG: невозможно получить параметры void**, чтобы сохранить их значение