Unit 2. Developing Programming ToolsRevision Date: Jul 27, 2017 (Version 2.1)
In this lesson, students will be introduced to the concepts of iteration and
Note: Turtle graphic examples in this lesson work with the community version of the PyCharm IDE and Python 3.4.1.
Students must understand that programs use the concept of iteration to perform repeated tasks.
Student computer usage for this lesson is: required
In the Lesson Resources folder:
Useful additional resources:
Journal: Think about events in your life that require a repeated action. They could be something simple such as eating a bowl of cereal. List two events in your life that require an action to be repeated. What is the action? What prompts the need for the action to happen? How often does the action happen?
Note: Students will extend their reflections later in the lesson.
Materials: 5-10 objects that can be stacked (lego, duplo blocks, plastic cups…)
The activity: Place the objects on a table.
1.Say: “At the conclusion of this activity, all of the objects will be stacked.”
Chose one object to begin with.
2. Say: “I will start with this object and I will continue to stack until there are no single objects left on the table. How many times do you think I will stack an object? Why?”
3. Ask: "Are there any single objects on the table?”
Students should answer yes. Stack one object on your beginning object
4. Ask “ Are there any single objects on the table?”
Students should answer yes. Stack one more object on your started stack. Continue to ask if there are any single objects on the table until the stack is completed and there are no more single objects on the table. Keep a tally of how many times you repeated the process.
5. Ask: “How many times did we repeat the process? Did your prediction match the result?"
6. Explain to the students how the activity represents the concept of iteration and continue into the discussion of iteration.
Computers are used in assembly lines and other places with lots of repetition because they can be almost perfectly accurate thanks to sensors that can be calibrated to the millimeter, and without needing to take a break.
Choose one of the events you wrote about in your previous journal entry. Take a moment to write the pseudocode for the repetitive action associated with that event.
Note: Check for understanding while students are working.
Example: Eating a slice of pizza:
While pizza on plate
pick up from plate
take a bite
place on plate
bite is consumed
This guided activity introduces students to
for loops using turtle graphics.
(See handout in Lesson Resources folder: Turtle Graphics Guided Activity: The for loop)
Give students the following code stem. Have the students alter the code to perform the listed tasks.
import turtle # Allows us to use the turtles library
window = turtle.Screen() # Creates a window to display graphics
bob = turtle.Turtle() # creates a turtle named bob
#Write your code here
window.exitonclick() # Exits the window when clicked
1. Have the turtle draw a triangle using a turtle
2. Now that you know how to add turtles and program them to draw lines repeatedly, use your imagination and creative ability to create your own picture using multiple
for loops and turtles.
Journal: In your journal summarize the process you used to create your picture. What problems did you encounter? What concepts do you need clarified?
Students can be given a copy of the guided activity handout to follow along.
a variety of checking for understanding techniques
Students will use for loops and turtle graphics to create graphic representations of iteration. They modify a code stem using turtle graphics to:
1. draw a triangle
2. draw a picture using multiple for loops and turtles.