How can I unload a DLL using ctypes in Python?

mydll = ctypes.CDLL('...')
del mydll
mydll = ctypes.CDLL('...')

mydll = ctypes.CDLL('./mylib.so')
handle = mydll._handle
del mydll
while isLoaded('./mylib.so'):
    dlclose(handle)

def isLoaded(lib):
   libp = os.path.abspath(lib)
   ret = os.system("lsof -p %d | grep %s > /dev/null" % (os.getpid(), libp))
   return (ret == 0)

def dlclose(handle)
   libdl = ctypes.CDLL("libdl.so")
   libdl.dlclose(handle)