尝试使用正确的定义:
class MODULEENTRY32(Structure):
_fields_ = [( 'dwSize' , DWORD ) ,
( 'th32ModuleID' , DWORD ),
( 'th32ProcessID' , DWORD ),
( 'GlblcntUsage' , DWORD ),
( 'ProccntUsage' , DWORD ) ,
( 'modBaseAddr' , POINTER(BYTE) ) ,
( 'modBaseSize' , DWORD ) ,
( 'hModule' , HMODULE ) ,
( 'szModule' , c_char * 256 ),
( 'szExePath' , c_char * 260 ) ]