Investigate using conditional statements with loops.
Questions to investigate
• Why would a programmer combine an if/elif/else conditional statement with a loop?
• Ensure SPIKE Prime hubs are charged, especially if connecting through Bluetooth.
• Ensure students have built the Kiki, the Dog model, which was used in the Guess Which Color lesson.
(Group Discussion, 5 minutes)
Engage students in thinking about choosing from multiple options.
Prompt students to brainstorm how they make a choice when presented with several options. Ask students to image they are at a breakfast buffet with as many breakfast options as they can think of. How do they decide which things to eat? Ask students to select three items that they would choose to eat.
Let students share their choices. What influences help make their choices (mood, time, favorites, etc.)? Discuss how making a plate of food at the buffet is similar to creating a code that allows you to choose some items (add to the plate) while not choosing others (skip them in line).
(Small Groups, 20 minutes)
Students will explore programming the Kiki model to react to colors according to conditions set in a loop.
Direct students to open their saved program for the Guess Which Color lesson. Students should connect their hub. Consider having students run the program one time to remember how it works.
Using a loop with an if/elif/else statement
Ask students to think about how they could modify the program used in the Guess Which Color lesson to repeat the condition allowing the program to identify more than one color. Students should recognize that a while loop will allow the color sensor to continue to react to the color read according to the conditions set.
Ask students to update their flowchart from the Guess Which Color lesson or create a new flowchart to show how the program should work.
Allow students time to modify their program and try it. Remind students to watch the console for error messages. Suggest to students to save this as a new program so as not to lose the original program.
from spike import PrimeHub, App, ColorSensor hub = PrimeHub() app = App() color_sensor = ColorSensor('B') \#While the condition continues to be true, repeat the if/elif/else statement. while True: color=color_sensor.wait_for_new_color() \#if the color is blue, play bird sound and write "detected blue" in the console. if color == 'blue': app.play_sound('Bird') print('Detected', color) \#if the color is green, play angry cat sound and write "detected green" in the console. elif color == 'green': app.play_sound('CatAngry') print('Detected', color) \#if the condition is not met, play wobble sound and write “wrong color detected” in the console. else: app.play_sound('Wobble') print('Wrong Color Detected')
Review the program with students. Discuss what changed as a result of having a loop in the program. Students should see that the loop allows the program to continue running after the first color is detected, which means the program will continue to react when a new color is presented.
Play a Guessing Game
Have students remove the other two colors of 2x4 bricks from their set. Have students rearrange their model to allow all five colors to fit. Students should rework their program to include a new condition for reading each color. Prompt students that more than one elif statement can be included. Working together have students program each brick to make a different sound.
from spike import PrimeHub, App, ColorSensor hub = PrimeHub() app = App() color_sensor = ColorSensor('B') \#Describe how each color makes the model react while True: color=color_sensor.wait_for_new_color() if color == 'blue': app.play_sound('Bird') print('Detected', color) elif color == 'green': app.play_sound('CatAngry') print('Detected', color) elif color == 'red': app.play_sound('Snoring') print('Detected', color) elif color == 'violet' app.play_sound('Moo') print('Detected', color) elif color == 'yellow' app.play_sound('DogBark1') print('Detected', color) else: app.play_sound('Wobble') print('Wrong Color Detected')
Each partner will take a turn being the game master and the other partner will play the guessing game. Without Partner 2 looking at the model, Partner 1 should play the program allowing the model to scan each color of the 2x4 bricks chosen. Partner 1 will get to decide which colors to scan. Partner 2 can listen to the sounds played in order to guess the color combination. Partner 2 can either write the color order down or use other pieces from the set to indicate the color order.
Have students check the guess at the end of the game and then switch partners.
(Whole Group, 5 minutes)
Discuss with students how the program worked.
Ask students questions like:
• How can a loop and conditional statement work together in one program?
• How is this program using more than one conditional statement?
Remind students that the while loop actually sets up a conditional statement as well. While that section of code is true, it will continue to repeat.
• How many conditions can you set in one program?
• When will the program end?
(Small Groups, 10 minutes)
Challenge students to try a new game where they are not detecting colors, but checking for bugs.
Show students each program and error message. Have students discuss what needs to change in each code to fix the bug or add the missing code. Consider making the changes as a class and ensuring the program runs correctly after each change.
Debugging Activity 1:
from spike import PrimeHub, App, ColorSensor hub = PrimeHub() app = App() color_sensor = ColorSensor('B') \#Describe how each color makes the model react color=color_sensor.wait_for_new_color() \#If the color is blue, play the bird sound and print “detected blue” in the console if color == 'blue': app.play_sound('Bird') #If the color is not blue, play the dog barking sound and print “what happened?” in the console else app.play_sound('DogBark1') File "lib/hub/flash/programrunner/__init__.py", line 1, in start_program File "./projects/23100.py", line 15 SyntaxError: invalid syntax
Students should recognize that the error is in line 15 from the error message. The invalid syntax means that we have not formatted something in the code correctly. Looking at line 15, students should notice that the else statement should have a colon at the end (:) with the statement of what to do as the else written on the next line with an indent.
Debugging Activity 2
from spike import Motor, PrimeHub \# Initialize the Hub and motor hub = PrimeHub() motor = Motor('F') \# This will make the hand open once to start motor.run_for_seconds(1, 75) while True: hub.left_button.wait_until_pressed() motor.set_stall_detection(False) motor.start(-75) hub.left_button.wait_until_released() motor.set_stall_detection(True) motor.start(75) File "lib/hub/flash/programrunner/__init__.py", line 1, in start_program File "./projects/52757.py", line 11 SyntaxError: invalid syntax
Students should recognize that the error is in line 11 as indicated in the error message. The conditional statement created by the while loop is not reading the condition because the lines of code for the condition are not indented. To fix the program, students need to indent all the lines of code needed for the conditional (lines 11-13).
Ask students to indent line 11 and only line 11. Run the program again. Students will receive a new error message.
File "lib/hub/flash/programrunner/__init__.py", line 1, in start_program File "./projects/4369.py", line 15 IndentationError: unexpected indent
Students should recognize that there is still an error in the code. By indenting line 11, we completed the conditional statement. The condition reads line 11 and then ends because line 12 is not indented. However, when the program reads line 15, it is confused why this line is indented. The error message reads “unexpected indent” to give us a hint about it.
Missing Code Activity
from spike import PrimeHub, App, ColorSensor hub = PrimeHub() app = App() color_sensor = ColorSensor('B') \#Describe how each color makes the model react color=color_sensor.wait_for_new_color() if color == 'blue': app.play_sound('Bird') elif
Discuss this program with students. Ask students what is missing to make this a complete program. Similar to debugging, you can run the program and receive an error message.
File "lib/hub/flash/programrunner/__init__.py", line 1, in start_program File "./projects/23262.py", line 13 SyntaxError: invalid syntax
In this case, the program sends an error for line 13 because the elif statement is not defined. Students need to add something that sets the new condition if the original condition is read as false.
Ask students to add a piece of code into the elif statement and try the program again. Students might have indicated a need to add to the else statement as well. If students run the new program, they will see a new error message to add a line of code to the else statement as well. Tell students that this error message did not show up before because the program will read the first error message and then stop. This means that additional messages are not initially called out.
(Group Exercise, 5 minutes)
Discuss the program with students.
Ask students questions like:
• How can a loop and conditional statement work together in one program?
• What actions should you take when you receive an error message?
• How many elif statements can you include in a program?
Have students answer the following in their journals:
• What did you learn today about adding multiple conditions in one program?
• What characteristics of a good teammate did I display today?
• Ask students to rate themselves on a scale of 1-3, on their time management today.
• Ask student to rate themselves on a scale of 1-3, on their materials (parts) management today.
Hỗ trợ giáo viên
• Write code that uses multiple condition statements using if/elif/else programming.
• Add a loop to code.
• Debug coding that has incorrect/missing syntax, missing code, or incorrect indention.
• SPIKE Prime sets ready for student use
• Devices with the SPIKE App installed
• Student journals
2-CS-02 Design projects that combine hardware and software components to collect and exchange data.
2-AP-10 Use flowcharts and/or pseudocode to address complex problems as algorithms
2-AP-13 Decompose problems and subproblems into parts to facilitate the design, implementation, and review of programs.
2-AP-16 Incorporate existing code, media, and libraries into original programs, and give attribution.
2-AP-17 Systematically test and refine programs using a range of test cases.
2-AP-19 Document programs in order to make them easier to follow, test, and debug.