For example, using an index of -1 is a handy way to grab the last item from a list no matter the size of the list. In that case, list_of_ints[-1] yields 3 , and list_of_objects[-1] yields None .

Items in a listbox are organized in an zero-indexed format, similar to the Python list. So, the first item resides in the first index, which is the number 0. The second item is at the number 1 ...