Run Python script at startup in Ubuntu

I have a short Python script that needs to run at startup - Ubuntu 13.10. I have tried everything I can think of but can't get it to run. The script: #!/usr/bin/python import time with open("/home/username/Desktop/startup.txt", 'a') as f: f.write(str(time.time()) + " It worked!") (The actual script is a bit different, as I'm just using this for testing purposes, but you get the idea.) I've tried all of the following, with no luck: - Put the command `python startuptest.py` in `crontab`, as `@reboot python /home/username/Documents/startuptest.py`, both as the regular user and as `sudo` - Put the command `python /home/username/Documents/startuptest.py` in `/etc/rc.local` - Opened Ubuntu's Startup Applications and put the command there - Done all of the preceding, putting the command into a shell script and calling that shell script instead Nothing works. I get the feeling I'm missing something simple. Any ideas? (The script runs fine if I just run the command from a terminal.)