The Debugging Method

Debugging is a method, not luck.

1. Reproduce — find the smallest input that triggers the bug.
2. Read — traceback? Wrong output? Start from the evidence.
3. Locate — narrow the search: does the bug exist in the input, the middle step, or the output? Print or assert along the pipeline until the region shrinks.
4. Understand — never fix what you cannot explain. "Delete this line, it seems to help" is how bugs become ghosts.
5. Fix and verify — one change at a time, then confirm the exact failure is gone AND nothing else broke.

Tools you already have

• print(type(x), repr(x)) — see the real value, not the format you assume.
• assert condition, "message" — state what MUST be true; Python checks it.
• Explaining the code out loud (even to a rubber duck) exposes wrong assumptions.

The Bug Hunt below is this method, drilled: each broken program is a real bug pattern you will meet in your own code.