Lesson 2.05: Lists

Learning Objectives

Students will be able to...

• Define and identify: list, item, index, integer
• Be able to access items from a list using the index
• Create lists of different types
• Use the length function

Materials/Preparation

• Do Now
• Lab
• Solution
• Associated Reading - section 2.4 of Book
• Read through the do now, lesson, and lab so that you are familiar with the requirements and can assist students

Pacing Guide

Instructor's Notes

1. Do Now
   • Students follow instructions to create lists and use the len function.

2. Lesson

   • Ask students to recall what a list is, and how lists were used in Snap!

     • A list is a sequence of values. In a list, they can be any type. The values in a list are called elements or items.
     • In Python, to create a list you must enclose items in square brackets.
     • Emphasize that you can have lists of any type (int, float, string, etc). You can even have lists within lists (more on that later...)
     • Remind students of lists in Snap!

     

   • Ask students what len does when they used it in the Do Now.
   • Ask students how they tried to print the first item from a list. Was this what they were expecting?
     • index: a map from the position in the list to the element stored there.
     • 0-index: lists are 0 indexed. So the first element in the list is at the 0-index
     • Out-of-bounds: what happened when you tried to index into a list that was too long?
     • Snap Equivalent:
     • Ask students how they would access the last item in a list of unknown length. (Use the length function!)
       • Ask students to write on the board how they got the last element of a list. Ask another student to write how they would get the second to last element of the list and so on.
     • After accessing any list element you can change it. Take a moment to demonstrate this syntax before starting the lab.
3. Lab
   • Practice accessing and updating items in a list
   • Implement program from last lab using lists
   • Create a quiz program
4. Debrief
   • Check student progress and completion of the lab, wrap up by taking any final questions.

Accommodation/Differentiation

If students are moving quickly, you can introduce the topic of nested lists. Start off with a simple nested list like ['a', 'b', 'c', [1, 2, 3]]. Ask the students to guess the length. Ask the students to guess how they would access the item '1' from that list!