GetNumDevices
Description:
                  This function returns the number of devices connected to the host.
Prototype: 
                  STATUS GetNumDevices (LPDWORD NumDevices)
Parameters: 
                   1. NumDevices—Address of a DWORD variable that will contain the number of devices connected on return.
2.2 Return Value: STATUS = SI_SUCCESS or
                           SI_DEVICE_NOT_FOUND or
                           SI_INVALID_PARAMETER

#!/usr/bin/python
import ctypes
DWORD = ctypes.c_ulong
LPDWORD = PDWORD = ctypes.POINTER(DWORD)
HANDLE = ctypes.c_void_p
mylib = ctypes.cdll.LoadLibrary('./lib/mylib.so')
numdev = LPDWORD
a = mylib.GetNumDevices(numdev)
print a
print numdev
print "The End."

/py/mod# 
./index.py
Traceback (most recent call last):
  File "./index.py", line 17, in <module>
    a = mylib.GetNumDevices(numdev)
ctypes.ArgumentError: argument 1: <type 'exceptions.TypeError'>: Don't know how to convert parameter 1

numdev = DWORD(0)
a = mylib.GetNumDevices(ctypes.byref(numdev))