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Python Course in 4 to 6 Weeks – Lesson 12: Error Handling in Python

🛡️ Python Course in 4 to 6 Weeks – Lesson 12: Error Handling in Python

Welcome to Lesson 12 of our Python Course in 4 to 6 Weeks! In this lesson, we’ll learn how to write safer and more stable Python code using error handling techniques. Mistakes happen — and your code needs to handle them gracefully.

✅ What You'll Learn

  • What are exceptions and errors?
  • Using try, except to handle errors
  • Using finally and else blocks
  • Common Python errors and how to fix them
  • Writing custom error messages

🚨 Common Errors in Python

  • ZeroDivisionError – dividing by 0
  • ValueError – invalid input type
  • TypeError – mismatched data types
  • FileNotFoundError – trying to open a missing file

🧯 Using try-except

try:
    x = int(input("Enter a number: "))
    result = 10 / x
    print("Result:", result)
except ZeroDivisionError:
    print("❌ You can't divide by zero!")
except ValueError:
    print("❌ Please enter a valid number.")

📌 Using else and finally

try:
    f = open("file.txt")
except FileNotFoundError:
    print("File not found.")
else:
    print("File opened successfully!")
    f.close()
finally:
    print("This block always runs.")

⚠️ Tips for Safe Coding

  • 🔒 Always validate user input
  • 💬 Use custom messages to help users understand errors
  • 🚫 Don’t leave broad except: without specifying the error type

🧪 Practice Challenge

Create a Python file named safe_divider.py that:

  • Asks the user for two numbers
  • Tries to divide them
  • Handles ZeroDivisionError and ValueError
  • Prints a custom success or failure message

📥 Tools You'll Need

📌 Final Words

With error handling, your programs become stronger and more user-friendly. Always remember: good code doesn’t just work — it fails safely. Up next, we’ll cover how to work with Python modules and libraries to use and organize external code.

🔗 Coming Next:

Lesson 13: Modules & Libraries – Organize and Reuse Python Code 📦

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