Lesson 12: Practice with Conditionals & While Loops

Lesson 12: Practice with Conditionals & While Loops#

Owner: đź’¤ Luce, Jason

Overview & Introduction#

This lesson provides a focused review and practice session combining two previously learned concepts: conditional statements and while loops. Students have already seen how if statements allow programs to make decisions and how while loops enable repeated execution based on a condition.

The goal of this lesson is to strengthen fluency in using these tools together to solve practical programming problems. Through guided and independent exercises, students will learn how conditional logic interacts with looping structures—particularly how conditions can be used to start, control, and terminate loops correctly.

By the end of this class, students will be comfortable tracing, debugging, and writing small interactive programs that rely on both conditionals and loops.

Learning Objectives#

By the end of this 50-minute session, students will be able to construct interactive programs that combine conditionals and while loops, trace and debug programs that contain nested or repeated conditions, explain how loop conditions depend on variable updates within the loop body, and apply conditional logic to manage user input and control repetition. Each objective is directly supported through guided practice and an end-of-class reflection exercise.

Prerequisites#

Students should already be able to write simple if/elif/else statements and basic while loops. They should also understand Boolean operators ( and, or, not) and comparison operators ( ==, <, >=, etc.).

Each student needs a computer with Python installed (e.g., Thomy, IDLE, or Replit).

The instructor should prepare a projector or shared screen for code demonstrations, and provide worksheets or an online notebook for in-class exercises.

This lesson works equally well in person, hybrid, or remote environments.

Lesson Outline#

Ask students:

Begin the class with a short code-reading exercise to reactivate prior knowledge.

Display a short Python snippet such as:

x = 0
while x < 5:
    if x % 2 == 0:
        print(x, "is even")
    else:
        print(x, "is odd")
    x += 1

Ask students to predict what the code will print and explain why.

Use this as a quick refresher to illustrate that conditions inside loops are re-evaluated each time through the loop, and that updates to variables (like x += 1) determine when the loop ends.

Discuss how omitting or incorrectly updating the loop variable could cause an infinite loop. This conversation reinforces how conditional and iterative logic work together.

Transition from review to demonstration.

Explain that many real-world programs use conditional loops, meaning loops that depend on decisions made during runtime.

Walk through an example of input validation, a common pattern combining both conditionals and while loops:

password = ""
while password != "python":
    password = input("Enter the password: ")
    if password != "python":
        print("Incorrect. Try again.")
print("Access granted!");

Guide students in reasoning through the logic: the condition password != "python" keeps the loop running, while the conditional inside the loop controls the feedback message.

Highlight how nested logic can make programs responsive to user behavior.

Then, show an edge case—what if the loop condition is written incorrectly?

while password == "python":

This subtle change prevents the loop from running at all.

Use this as an opportunity to discuss debugging strategies and to model deliberate, step-by-step testing.

Shift to hands-on participation. Have students write short programs following the instructor’s verbal prompts. Examples may include:

  • Guess the Number Game (Part 1) – The computer stores a secret number between 1 and 10. The player keeps guessing until they find it, with feedback for each attempt.

Example structure:

secret = 7
guess = 0

while guess != secret:
    guess = int(input("Guess a number between 1 and 10: "))
    if guess < secret:
        print("Too low.")
    elif guess > secret:
        print("Too high.")
print("You got it!")

Discuss how to ensure the loop condition checks the user’s input correctly and why indentation and ordering matter.

Encourage students to predict outputs, modify the code to add conditions (e.g., invalid input handling), and share their results with a partner.

Students now apply what they’ve practiced to solve a new problem independently.

Challenge prompt:

Write a program that asks the user for a positive number and prints all the even numbers up to that number. If the user enters a negative value, ask again until they enter a positive one.

This task combines conditional checking, loop control, and iteration over a changing variable.

Encourage students to test edge cases—such as entering zero or non-numeric input—and think about how to modify their code to handle unexpected inputs gracefully.

End with a brief discussion and self-assessment. Ask:

  • “How did the conditions inside your loop control when it stopped?”

  • “What errors or infinite loops did you encounter, and how did you fix them?”

Then, assign a short exit task:

Write a while loop that asks the user to enter a number between 1 and 5. If they enter an invalid number, print an error and ask again. The loop ends only when they enter a valid number.

This problem directly measures understanding of condition-driven repetition and validates the core learning objectives.

Throughout the session, formative assessment occurs through class discussion, peer debugging, and instructor observation. Summative evaluation is based on whether students can write functioning, logically sound code for the exit problem and describe how their conditions control loop flow.

This lesson reinforced how conditionals and while loops complement one another in interactive programs. Students learned to trace logic, handle user input, and prevent infinite loops through deliberate variable control.

The next lesson will build on these skills by introducing nested loops and examining loop patterns, expanding the range of problems students can solve with iterative logic.

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