Restarting a self-updating python script

Question

I have written a script that will keep itself up to date by downloading the latest version from a website and overwriting the running script.

I am not sure what the best way to restart the script after it has been updated.

Any ideas?

I don't really want to have a separate update script. oh and it has to work on both linux/windows too.

Answer 1

In Linux, or any other form of unix, os.execl and friends are a good choice for this -- you just need to re-exec sys.executable with the same parameters it was executed with last time (sys.argv, more or less) or any variant thereof if you need to inform your next incarnation that it's actually a restart. On Windows, os.spawnl (and friends) is about the best you can do (though it will transiently take more time and memory than os.execl and friends would during the transition).

Answer 2

The CherryPy project has code that restarts itself. Here's how they do it:

    args = sys.argv[:]     self.log('Re-spawning %s' % ' '.join(args))      args.insert(0, sys.executable)     if sys.platform == 'win32':         args = ['"%s"' % arg for arg in args]      os.chdir(_startup_cwd)     os.execv(sys.executable, args) 

I've used this technique in my own code, and it works great. (I didn't bother to do the argument-quoting step on windows above, but it's probably necessary if arguments could contain spaces or other special characters.)