An example launchd plist file. The launchd agent will first change the working directory, set the arguements and, execute a python script. This is a minimalist launchd template that can easily be expanded upon.

com.python.launchd.agent.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Label</key>
	<string>com.nuntium.fetchnews.agent</string>
	<key>ProgramArguments</key>
	<array>
		<string>/usr/local/bin/python3</string>
		<string>nuntium.py</string>
		<string>--fetch-news</string>
	</array>
	<key>RunAtLoad</key>
	<true/>
	<key>StartInterval</key>
	<integer>600</integer>
	<key>WorkingDirectory</key>
	<string>/Users/jessefogarty/Google Drive/github/nuntium/nuntium</string>
</dict>
</plist>

I wrote this in order to automate my Nuntium project. Oh how I relish crontab so much more after this.

end result is akin to running:

$ cd /Users/jessefogarty/Google Drive/github/nuntium/nuntium
$ python3 nuntium.py --fetch-news

every 10 minutes.

Where to install your plist file

~/Library/LaunchAgents/

Loading your plist file

$ cd ~/Library/LaunchAgents/
$ launchctl load <plist>

Default logs

When checking the system.log output you know you plist was loaded fine IF there's no error to check run:

$ cd /var/log
$ grep '<plist file name>' system.log

Feel free to include a snippet of your plist code if you're having trouble and I'll do my best to help you fix it.

Enjoy!