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Debugging  and  Refactoring

Debugging  and  Refactoring

Learn debugging and refactoring with Copilot to fix bugs, clean code, and build reliable, maintainable projects.

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Why debug and refactor?

Even with solid unit tests, bugs can still sneak into the runtime. Debugging is about finding and fixing those issues. Refactoring, however, focuses on improving messy or overly complex code, which helps prevent future bugs and makes the code easier to maintain.

Note: Refactoring isn’t just about cleaning code; it makes it faster for new developers to read, understand, and contribute. Well-organized code helps teams move quicker and onboard new teammates with less confusion.

Runtime error hunt

Let’s explore how to find and fix bugs affecting your program during runtime.

Bug scenario: Infinite loop in triple while nest

Here’s a classic example where a missing update creates an infinite loop—let’s debug it together.

def has_triplet_sum(nums: list[int], target: int) -> bool:
    i = 0
    while i < len(nums):
        j = 0
        while j < len(nums):
            k = 0
            while k < len(nums):
                if nums[i] + nums[j] + nums[k] == target:
                    return True
                k += 1
            j += 1
    return False
print(has_triplet_sum([1, 2, 3], 6))
Infinite loop in triple while nest

Task:

  1. Run this code locally.

  2. Open Copilot chat and prompt:

Context: has_triplet_sum hangs on sample input.
Instruction: Identify the loop causing the infinite iteration and propose a fix.
Constraint: Explain the root cause in one paragraph.

  1. Copilot ...