Hi Sybren and Wolfram, thank you very much for the time.sleep() tip. My program reads like this now. import os import time WINDOWS_SHARE = 'C:\\Temp' while 'transfer.lock' in os.listdir( WINDOWS_SHARE ): print "Busy, please wait..." time.sleep(10) f = open(WINDOWS_SHARE + '/myfile', 'w') f.write("test 123") f.close() print "Done!" Nico