Python threading.Timer not waiting before executing function

Question

I have thrown together a quick threading test:

import threading

def test():
    print "it don't work"
while True:
    threading.Timer(1, test).start()

It runs test, but it doesn't wait. What's wrong?

Runs fine (as expected) in Pyhton27. But you should put a time.sleep in that loop, to avoid killing the CPU. — CristiFati
– CristiFati, Commented Apr 27, 2017 at 17:54

napuzba · Accepted Answer · 2017-04-27 18:13:44Z

2

In each loop iteration, you start a new thread. Therefore you will reach the limit of allowed thread and you will get an exception : can't start new thread.

while True:
    threading.Timer(1, test).start()

You can add global flag and wait until the function is executed - You should use time.sleep to avoid busy waiting.

a = False
def test():
    global a
    print("hallo")
    a = True
threading.Timer(10, test).start()
while not a:
    time.sleep(1)
print('done')

edited Apr 27, 2017 at 18:13

answered Apr 27, 2017 at 17:56

napuzba

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2 Comments

Will6316 Over a year ago

I guess that I should have been more specific. I am trying to put this timer in a game event loop, so it needs to run serpratly from the rest of the program.

napuzba Over a year ago

Well, After calling threading.Timer.start - you have two threads , the main thread and a thread which run the function in delay and exits.

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