Here is a simple trick that I used to restart my python script after unhandled exception.
Let’s say I have this simple script called test.py that I want to run forever. It will just wait 2 seconds and throw an error.
import time
time.sleep(2)
raise Exception("Oh oh, this script just died")
I use the following script called forever in the same directory:
#!/usr/bin/python
from subprocess import Popen
import sys
filename = sys.argv[1]
while True:
print("\nStarting " + filename)
p = Popen("python " + filename, shell=True)
p.wait()
It uses python to open test.py as a new subprocess. It does so in an infinite while loop, and whenever test.py fails, the while loop restarts test.py as a new subprocess.
I’ll have to make the forever script executable by running chmod +x forever. Optionally forever script can be moved to some location in the PATH variable, to make it available from anywhere.
Next, I can start my program with:
./forever test.py
Which will result in the following output:
Starting test.py
Traceback (most recent call last):
File "test.py", line 4, in <module>
raise Exception("Oh oh, this script just died")
Exception: Oh oh, this script just died
Starting test.py
Traceback (most recent call last):
File "test.py", line 4, in <module>
raise Exception("Oh oh, this script just died")
Exception: Oh oh, this script just died
Starting test.py
As you can tell, this script will run repeatedly, until it is killed with ctr+c.
Courier Natix says
April 11, 2019 at 5:14 pmI’m trying this out now, I have two discord bots and recently they’ve been crashing at random without saying why, even with logging. I’ve been looking for a solution to my problem for weeks now and so far, your solution is working great! Thank you for sharing this!
kostas says
March 27, 2019 at 3:33 amgreat
Thanks a lot
fakename. says
January 7, 2019 at 9:03 pmThis is very helpful. Thank you.
Erdener says
December 27, 2018 at 2:47 pmAlex thanks for your guidance.
It worked in Debian GNU/linux machine but I’m getting error on Linux 18.04. The error message:
./forever.py: /usr/bin/python: bad interpreter: No such file or directory
When I removed first line the error was being like that:
./forever.py: line 2: from: command not found
./forever.py: line 3: import: command not found
./forever.py: line 4: import: command not found
./forever.py: line 6: filename: command not found
./forever.py: line 8: syntax error near unexpected token
"\nStarting "'print(“\nStarting ” + filename)’./forever.py: line 8:
What can be the problem?
Alex Kras says
January 8, 2019 at 10:26 amNot sure, do any other python scripts work?
Anthony Nardelli says
December 7, 2018 at 11:56 amHello, I have an implementation where a python script calls two other scripts, is there a way to adapt your implementation with my example?
HITESH SALAVI says
August 23, 2018 at 5:02 amI have a flask framework implementation. I have a global variable which is being used in a route(ie. /xyz) and nowhere else.
When I don’t run /xyz, the global variable gets vanished(my may or may not accurate #AfterDebuggingConclusion). How can I keep the variable in the memory if my conclusion is right?
Alex Kras says
August 23, 2018 at 10:18 amHmm, I think if you declare it outside of scope of this /xyz method it should exist even if method did not run. Then you can reference it inside of function by declaring it
global xyz.
Сергей Мищенко says
August 12, 2018 at 5:17 amThank You VERY MUCH! <3
Ehsan Derakhshan says
July 23, 2018 at 12:55 amThis script help me a lot my friend thank you so much.
10basetom says
June 25, 2018 at 12:21 amThanks for this great tip. I’m trying to output the subprocess script’s
printstatements to the screen, but so far no success :(. Here’s what I have so far:import subprocess
import sys
filename = ‘my_script.py’
while True:
print(‘Starting ‘ + filename + ‘ …’)
p = subprocess.Popen(‘python ‘ + filename, shell=True, stdout=subprocess.PIPE)
(output, err) = p.communicate()
print(output)
p.wait()
It would be awesome if you could point me in the right direction. Thanks!