Перезапуск скрипта python при ошибке

asked Mar 15, 2016 at 17:42

It depends on what you mean by «restart itself.» If you just want to continuously execute the same code, you can wrap it in a function, then call it from within a while True loop, such as:

>>> def like_cheese():
...     var = input("Hi! I like cheese! Do you like cheese?").lower()  # Corrected the call to `.lower`.
...     if var == "yes":
...         print("That's awesome!")
...
>>> while True:
...     like_cheese()
...
Hi! I like cheese! Do you like cheese?yes
That's awesome!
Hi! I like cheese! Do you like cheese?yes
That's awesome!

If you want to actually restart the script you can execute the script again, replacing the current process with the new one by doing the following:

#! /bin/env python3
import os
import sys

def like_cheese():
    var = input("Hi! I like cheese! Do you like cheese?").lower()
    if var == "yes":
        print("That's awesome!")

if __name__ == '__main__':
    like_cheese()
    os.execv(__file__, sys.argv)  # Run a new iteration of the current script, providing any command line args from the current iteration.

This will continuously re-run the script, providing the command line arguments from the current version to the new version. A more detailed discussion of this method can be found in the post «Restarting a Python Script Within Itself» by Petr Zemek.

One item that this article notes is:

If you use the solution above, please bear in mind that the exec*()
functions cause the current process to be replaced immediately,
without flushing opened file objects. Therefore, if you have any
opened files at the time of restarting the script, you should flush
them using f.flush() or os.fsync(fd) before calling an exec*()
function.

answered Mar 15, 2016 at 17:55

or you can try

$ chmod a+x "name".py

Then, you can run the script via

$ ./daemon.py

In such a situation, to restart the script, use the following code:

os.execv(__file__, sys.argv)

Otherwise, when you run the script via

$ python daemon.py

use this code:

os.execv(sys.executable, ['python'] + sys.argv)

Either way, do not forget to import the sys module

exbctelexbctel

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ChrisChris

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You can wrap something in while True: to make it execute repeatedly, as True will always evaluate to True, like this:

while True:
    var = input("Hi! I like cheese! Do you like cheese?").lower() # <-- You had missed parentheses here        
    if var == "yes":
        print("That's awesome!")

There’s another issue with your code though; you haven’t called lower by putting parentheses after it.

answered Mar 15, 2016 at 17:44

asked Mar 15, 2016 at 17:42

It depends on what you mean by «restart itself.» If you just want to continuously execute the same code, you can wrap it in a function, then call it from within a while True loop, such as:

>>> def like_cheese():
...     var = input("Hi! I like cheese! Do you like cheese?").lower()  # Corrected the call to `.lower`.
...     if var == "yes":
...         print("That's awesome!")
...
>>> while True:
...     like_cheese()
...
Hi! I like cheese! Do you like cheese?yes
That's awesome!
Hi! I like cheese! Do you like cheese?yes
That's awesome!

If you want to actually restart the script you can execute the script again, replacing the current process with the new one by doing the following:

#! /bin/env python3
import os
import sys

def like_cheese():
    var = input("Hi! I like cheese! Do you like cheese?").lower()
    if var == "yes":
        print("That's awesome!")

if __name__ == '__main__':
    like_cheese()
    os.execv(__file__, sys.argv)  # Run a new iteration of the current script, providing any command line args from the current iteration.

This will continuously re-run the script, providing the command line arguments from the current version to the new version. A more detailed discussion of this method can be found in the post «Restarting a Python Script Within Itself» by Petr Zemek.

One item that this article notes is:

If you use the solution above, please bear in mind that the exec*()
functions cause the current process to be replaced immediately,
without flushing opened file objects. Therefore, if you have any
opened files at the time of restarting the script, you should flush
them using f.flush() or os.fsync(fd) before calling an exec*()
function.

answered Mar 15, 2016 at 17:55

or you can try

$ chmod a+x "name".py

Then, you can run the script via

$ ./daemon.py

In such a situation, to restart the script, use the following code:

os.execv(__file__, sys.argv)

Otherwise, when you run the script via

$ python daemon.py

use this code:

os.execv(sys.executable, ['python'] + sys.argv)

Either way, do not forget to import the sys module

exbctelexbctel

1951 silver badge9 bronze badges

ChrisChris

17.3k15 gold badges57 silver badges76 bronze badges

You can wrap something in while True: to make it execute repeatedly, as True will always evaluate to True, like this:

while True:
    var = input("Hi! I like cheese! Do you like cheese?").lower() # <-- You had missed parentheses here        
    if var == "yes":
        print("That's awesome!")

There’s another issue with your code though; you haven’t called lower by putting parentheses after it.

answered Mar 15, 2016 at 17:44

On Ubuntu (until 14.04, 16.04 and later use systemd) can use upstart to do so, better than a cron job. You put a config setup in /etc/init and make sure you specify respawn

It could be a minimal file /etc/init/testing.conf (edit as root):

chdir /your/base/directory
exec python testing.py
respawn

And you can test with /your/base/directory/testing.py:

from __future__ import print_function

import time

with open('/var/tmp/testing.log', 'a') as fp:
    print(time.time(), 'done', file=fp)
    time.sleep(3)

and start with:

sudo start testing

and follow what happens (in another window) with:

tail -f /var/tmp/testing.log

and stop with:

sudo stop testing

You can also add [start on][2] to have the command start on boot of the system.

answered Jan 5, 2014 at 7:59

You could also take a more shell oriented approach. Have your cron look for your script and relaunch it if it dies.

1. Create a new crontab by running crontab -e. This will bring up a window of your favorite text editor.

2. Add this line to the file that just opened

   */5 * * * * pgrep -f testing.py || nohup python /home/you/scripts/testing.py > test.out
   

3. Save the file and exit the editor.

You just created a new crontab which will be run every 5 minutes and launch your script unless it is already running. See here for a nice little tutorial on cron. The official Ubuntu docs on cron are here.

The actual command being run is pgrep which searches running processes for the string given in the command line. pgrep foo will search for a program named foo and return its process identifier. pgrep -f makes it search the entire command line used to launch the program and not only the program name (useful because this is a python script).

The || symbol means «do this if the previous command failed». So, if your script is not running, the pgrep will fail since it will find nothing and your script will be launched.

answered Jan 5, 2014 at 9:24

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answered Jun 15, 2017 at 20:00

answered Mar 8, 2019 at 19:28

ChrisChris

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There’s a Python module for that, forever.

The advantage being, hopefully, in using the same language for both the code and the watchdog. If it needs to be improved, one can find it in

cd $(python -c "import site; print(site.getusersitepackages())")

I’d install it with

python -mpip install --user --upgrade forever

and later use it with

python -mforever.run -t 9 -i 9 python script-to-watch.py

answered Feb 12, 2022 at 12:06