- intentional errorif you haven' received an index error in one of your programs yettry to make one happen change an index in one of your programs to produce an index error make sure you correct the error before closing the program summary in this you learned what lists are and how to work with the individual items in list you learned how to define list and how to add and remove elements you learned to sort lists permanently and temporarily for display purposes you also learned how to find the length of list and how to avoid index errors when you're working with lists in you'll learn how to work with items in list more efficiently by looping through each item in list using just few lines of code you'll be able to work efficientlyeven when your list contains thousands or millions of items