Teaching Debugging: How to Help Students Solve Their Own Coding Problems

One of the hardest lessons in teaching programming isn’t loops, functions, or even recursion – it’s teaching debugging. When students first start to code, the most common instinct is to write something, run it, and then stare in dismay when the computer throws a wall of red text back at them.

The temptation as a teacher is to swoop in and fix it. After all, you can see straight away that they’ve typed pritn instead of print. But solving it for them isn’t teaching – it’s firefighting. The ultimate goal is to help students learn how to identify and correct their own mistakes.

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Start with the Error Message

For beginners, error messages might be written in another language. Helping students slow down and read what the computer is actually telling them is the first step. Show them how to pick out the key parts of the message: the line number, the type of error, and what might have gone wrong.

For example:

NameError: name 'totl' is not defined

Instead of panicking, students can learn to ask: Where is this happening? What might I have misspelt?

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Think Like the Computer

Debugging means learning to step inside the computer’s shoes. Encourage students to walk through the code line by line and predict what should happen at each stage. Pseudocode, flow diagrams, or even just talking through it aloud helps them see where the logic goes astray.

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Break It Down

When a program doesn’t work, the whole thing can feel overwhelming. One useful strategy is “divide and conquer”: get students to comment out sections, print intermediate results, or test smaller chunks of code in isolation. This way, they narrow down the problem instead of getting overwhelmed by it.

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Normalise Mistakes

Perhaps the most important lesson: errors are not failures – they are part of the process. Every coder, from beginner to professional, spends a large chunk of time debugging. Remind students that if they’ve got an error message, congratulations – the computer has just given them a clue!

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Encourage Independence

Finally, resist the urge to fix things immediately. Instead, prompt with questions:

• What do you think that error means?

• What’s happening just before this line?

• What would happen if you printed out the value here?

With a bit of patience, students not only solve their current problem, but they also gain confidence to tackle the next one on their own.

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Debugging in Action: Classroom Examples

Example 1: String Concatenation vs Addition

num1 = input("Enter first number: ")
num2 = input("Enter second number: ")
total = num1 + num2
print("The total is", total)

The student enters 3 and 4 and expects 7, but gets:

The total is 34

• The program runs fine, but the logic is wrong.

• input() returns strings, so Python is joining text rather than adding numbers.

• Printing type(num1) shows it’s a str.

• Fix: convert inputs to integers.

num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))
print("The total is", num1 + num2)

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Example 2: A Syntax Error

for i in range(5)
    print(i)

Error message:

SyntaxError: expected ':'

• Python can’t run this at all – it’s missing a colon.

• Fix:

for i in range(5):
    print(i)

Lesson: syntax errors mean the computer literally doesn’t understand the instruction.

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Example 3: A Logic Error

def average(a, b):
    return a + b / 2

print(average(10, 20))

Expected answer: 15.
Output: 20.0.

• No error message – but the answer is wrong.

• Python follows operator precedence: 10 + (20/2).

• Fix:

def average(a, b):
    return (a + b) / 2

Lesson: logic errors are trickier – the program runs, but doesn’t do what you intended.

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Wrapping Up

Debugging isn’t just about fixing code – it’s about teaching problem-solving, persistence, and resilience. By encouraging students to:

• Read error messages carefully,

• Think like the computer,

• Test small sections of code, and

• Reflect on what went wrong,

…we equip them with a skill set that extends far beyond Python or Java. Debugging is really about learning how to think.

At Hemel Private Tuition, we encourage students to build, test, and play with code — because learning works best when it’s fun.