🔍 Python Traceback & Debugging Guide

Beginner-friendly documentation about Python tracebacks, exception debugging, and useful debugging patterns.

This document explains: - what a traceback is - how exceptions work - traceback module - extracting function names - debugging helpers - useful debugging patterns

---

📚 Table of Contents

• 📖 What is a Traceback?
• ⚠️ Basic Exception Output
• 🧠 Using traceback
• 📦 extract_tb()
• 🎯 Getting the Failed Function Name
• 🛠️ Useful Debugging Patterns
• 🎮 Real 42 Examples
• ⚠️ Common Beginner Mistakes
• 📚 Best Practices
• 📚 Final Notes

---

📖 What is a Traceback?

A traceback is: - Python's error report

It shows: - where the error happened - which functions were called - the exception type - the error message

---

Example Traceback

Traceback (most recent call last):
  File "main.py", line 10, in <module>
    divide(10, 0)
  File "main.py", line 5, in divide
    return a / b

ZeroDivisionError: division by zero

---

⚠️ Basic Exception Output

try:
    value = 10 / 0

except Exception as e:
    print(type(e).__name__)
    print(e)

---

Output

ZeroDivisionError
division by zero

---

🧠 Using traceback

import traceback

Useful for: - advanced debugging - custom error displays - logging

---

📦 extract_tb()

traceback.extract_tb() extracts traceback information.

---

Example

import traceback

try:
    value = 10 / 0

except Exception as e:

    tb = traceback.extract_tb(e.__traceback__)

    print(tb)

---

🎯 Getting the Failed Function Name

import traceback

try:
    value = 10 / 0

except Exception as e:

    tb = traceback.extract_tb(e.__traceback__)

    print(f"Failed on the function: {tb[-1].name}")
    print(f"{type(e).__name__}: {e}")

---

Example Output

Failed on the function: divide
ZeroDivisionError: division by zero

---

🛠️ Useful Debugging Patterns

Showing the Exception Type

print(type(e).__name__)

---

Showing the Exception Message

print(e)

---

Combining Both

print(f"{type(e).__name__}: {e}")

---

🎮 Real 42 Examples

Parser Errors

except Exception as e:

    tb = traceback.extract_tb(e.__traceback__)

    print(f"Failed on function: {tb[-1].name}")

---

Invalid Config

ValueError: Invalid WIDTH

---

Invalid Coordinates

MapParserError: Invalid coordinates

---

⚠️ Common Beginner Mistakes

❌ Using Bare except

Bad:

except:

---

❌ Ignoring Tracebacks

The traceback usually shows: - the REAL problem location

---

❌ Printing Huge Tracebacks Everywhere

Too much debugging output can: - clutter logs - make debugging harder

---

📚 Best Practices

• Read traceback lines carefully
• Look at the LAST function call first
• Print exception types clearly
• Use meaningful error messages
• Add debugging progressively

---

📚 Final Notes

Understanding tracebacks is essential for Python development.

Good traceback handling helps: - locate bugs quickly - improve error reporting - simplify debugging

---