Python While reach timeout

Question

I am running a Python script on a Windows machine that needs to exit from the while loop when timeout is reached or flag is True:

import time
start_time = time.time()
flag = False
timeout = 5

while time.time() < timeout + start_time:
    # DO something
    flag = True
    break

if flag is False:
   print(f"Timeout reached {timeout}")

With the current code, the timeout or the flag are not hit. Any hints of what it is wrong?

But since you set the flag to true, and break, it'd just do that "something" once. — ewokx, Sep 26 '22 at 09:10
I would need that something to run in a certain time. If exceeds it, print that message. — Albert, Sep 26 '22 at 09:23
The while-condition is checked once per iteration. It is not continually monitored while the block of code is executed. — khelwood, Sep 26 '22 at 09:33

Kyriakos Psarakis · Answer 1 · 2022-09-29T08:40:03.257

1

Try this solution without a loop, as shown here: https://stackoverflow.com/a/14924210/7988650

If you want to use a python package, you could use this one https://pypi.org/project/wrapt-timeout-decorator/ to make things shorter by just annotating your function with an @timeout()

import multiprocessing

def do_something():
    # Do something

if __name__ == '__main__':
    timeout = 5
    # Start do_something as a process
    p = multiprocessing.Process(target=do_something)
    p.start()
    # Wait for 5 seconds or until process finishes
    p.join(timeout)
    # If thread is still active
    if p.is_alive():
        print(f"Timeout reached {timeout}")
        # Terminate - may not work if process is stuck for good
        p.terminate()
        # OR Kill - will work for sure, no chance for process to finish nicely however
        # p.kill()
        p.join()

edited Sep 29 '22 at 08:40

answered Sep 26 '22 at 08:58

Kyriakos Psarakis

84
6

`if flag` in this case will execute when flag is true and I would like to print the message when flag is false. – Albert Sep 26 '22 at 09:23
The logic is wrong then because you are setting the flag to True when the timeout is reached i.e., the end of the while loop. – Kyriakos Psarakis Sep 26 '22 at 09:24
Thanks for your reply. The logic is correct because if `flag` sets to True I know that the `DO something` went successfully through the end and is executed before the timeout is reached. Nothing wrong with the logic. – Albert Sep 26 '22 at 09:26
It is the wrong way to do it, you cannot measure this the way you do it. Now that I understood your question, I will try to come up with a solution. – Kyriakos Psarakis Sep 26 '22 at 09:28
I know that this solution looks a bit complex, but there is no way to timeout a function (while loop) within that same function. – Kyriakos Psarakis Sep 26 '22 at 09:44
Thanks for solution. It wasn't working for me as I was using some Python library in DO SOMETHING that was in conflict with multithreading. I have added anyway for your answer +1 as this solution was working for others. – Albert Oct 03 '22 at 10:43

score 0 · Accepted Answer · answered Oct 03 '22 at 10:42

I am going to post the solution that I have found and worked for me as in the #DO SOMETHING section I had some blocks of code that were using some libraries that were in conflict with multithreading public library:

import time

MAX_TIMEOUT = 5

start_time = time.time()
while True:
    time_delta = time.time() - start_time
    while time_delta <= MAX_TIMEOUT:
        # DO SOMETHING
        finished = True
        break
        if finished:
           break
        if time_delta > MAX_TIMEOUT:
            print("Timeout reached.")
            break

If `do something` is a blocking operation, the `do something` won't be stoped once the timeout is reached, making the timeout, not a timeout but just a print statement. If the `multiprocessing` solution didn't work for you, I think giving a timeout decorator package a try would be better. — Kyriakos Psarakis, Oct 03 '22 at 11:55

score -1 · Answer 3 · answered Sep 26 '22 at 09:00

-1

It looks like you are adding up the start_time to timeout. Which makes it practically infinite.

try while time.time() < timeout:

answered Sep 26 '22 at 09:00

Yirnick van Dijk

9
2

Thanks for your reply. time.time() starts from the last epoch which is from 1st of January 1970 and is a big number. – Albert Sep 26 '22 at 09:30

Python While reach timeout

3 Answers3