using official CPython 3.2.3 with a simple demonstration script (attached) to demonstrate inconsistency between ctypes structures

from ctypes import *

class cbs( BigEndianStructure ):
    __slots__ = tuple()
    def __init__( self, *args, **kw ):
        super().__init__( *args, **kw )
        self.a = 11

class cls( LittleEndianStructure ):
    __slots__ = tuple()
    def __init__( self, *args, **kw ):
        super().__init__( *args, **kw )
        self.a = 11

class cs( Structure ):
    __slots__ = tuple()
    def __init__( self, *args, **kw ):
        super().__init__( *args, **kw )
        self.a = 11

try :
    cbs1=cbs()
except AttributeError as e:
    print(e)

try :
    cls1=cls()
except AttributeError as e:
    print(e)

try :
    cs=cs()
except AttributeError as e:
    print(e)



yields

'cls' object has no attribute 'a'
'cs' object has no attribute 'a'



I expect cbs to throw error too, but itwent through the initalization and silently ignored the __slots__ defined in the class

@hct I'm very sorry about the delay in getting back to you.  The reported bevaviour is the same with 3.4.1 and 3.5.0a0 on Windows 7.