Step-by-Step Guide to Debugging Python Code

Debugging is the process of finding and fixing bugs, essential for any developer. Here’s a simple step-by-step plan using just Python’s built-in tools.

1. Understand the error: Read the traceback message. It shows where the issue happened (file, line, error type). E.g., SyntaxError points to syntax issues, NameError to undefined variables.
2. Isolate the problem: Copy the suspicious code snippet to a separate file and run it alone. This checks if the error is local or depends on other parts.
3. Use print for checks: Add print() to output variable values before/after the spot. E.g., print(f"Variable x = {x}") shows what’s in x at that point.
4. Check data types: Use type(): print(type(var)). Often errors from expecting int but getting str.
5. Handle exceptions: Wrap code in try-except: try: [code] except Exception as e: print(e). This catches and shows details.
6. Step-by-step breakdown: Split function into smaller parts and test each. For loops — manually check first iteration.
7. Search docs: If built-in function error — check docs.python.org with keywords from traceback.
8. Test with small data: For data issues — use simplified input (e.g., list of 2 items instead of 1000).
9. Vary conditions: Change inputs to see when error disappears. This pinpoints the cause.
10. Fix and verify: After change, run full code and check for new issues.

This guide draws from real practices. For more exercises — check Trail Orbit.