A list uses square brackets to hold ordered items. Index zero names the first item; index -1 names the last. len(items) counts them. An out-of-range single index raises IndexError.
This is an editable worked demo. Edit main.py, press Run to compare the result, then Submit to check your small change. The next lesson transfers the idea to a different setting.
Change last_supply to select the last item; Run should print tape then Submit.
last_supply to the last item of supplies.