python - Setting ctypes.Structure default values -

this doesn't work:

class ifinfomsg(ctypes.structure):     _fields_ = [                  ('ifi_family',  ctypes.c_ubyte),                  ('__ifi_pad',   ctypes.c_ubyte),                  ('ifi_type',    ctypes.c_ushort),                  ('ifi_index',   ctypes.c_int),                  ('ifi_flags',   ctypes.c_uint),                  ('ifi_change',  ctypes.c_uint(0xffffffff))                ] 

it errors with:

  file "rtnetlink.py", line 243, in <module>     class ifinfomsg(ctypes.structure): typeerror: error when calling metaclass bases     second item in _fields_ tuple (index 5) must c type 

however can set values in __init__():

class ifinfomsg(ctypes.structure):     _fields_ = [                  ('ifi_family',  ctypes.c_ubyte),                  ('__ifi_pad',   ctypes.c_ubyte),                  ('ifi_type',    ctypes.c_ushort),                  ('ifi_index',   ctypes.c_int),                  ('ifi_flags',   ctypes.c_uint),                  ('ifi_change',  ctypes.c_uint)                ]      def __init__(self):         self.__ifi_pad = 0         self.ifi_change = 0xffffffff 

is 'correct' way this, via __init__?

your example errors because ctypes.c_uint(0xffffffff) not type. in class definitions has type (pointers pointer not pointer).

i think __init__ method use if fine. have wrapped large structures , typically use __init__ have done set default values.

in general if have control of c library wrapping think should not have default setting in both places (c , python). in 1 large library wrapped have access c created c functions "set_defaults" call __init__. way c users have access defaults , there 1 set of code maintain.