try: import thread except : import _thread as thread import threading from time import sleep def bar(y): z = 100 + y print("Z=%d"%z) t = None def foo(x): global t y = x + 1 print("Y=%d"%y) t = threading.Thread(target=bar, args=(y,)) t.start() id = thread.start_new_thread(foo, (1,)) while True: sleep(1)