You don't say exactly what you tried with launchd and cron, but I'd bet you weren't using either of them correctly. Both are oriented toward running single, isolated commands (/programs), not sequences of shell commands. While it's possible to do this with a single cron job or launchd item, it's going to be messy. The simplest thing would be to write a shell script that does the sequence you want (be sure to include a shebang at the beginning, and enable execute permission on the script with chmod +x /path/to/script
), and run that from either cron or launchd:
#!/bin/bash
source /.virtualenvs/myenvironment/bin/activate
cd ~/desktop/python/
python myscript.py
deactivate
I would not recommend using Automator to wrap the command sequence; it's designed for GUI-based scripting, and may not work right in a background-only job.